DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES

(Based on disallowable Instrument DI2013-44 ACT Environmental Flow Guidelines & recommendations in supporting report reviewing 2013 Environmental Flow Guidelines (Dusting et al. 2017)) © Australian Capital Territory, 2018

Photos taken by David Jenkins, Mark Jekabsons, Danswell Starrs and Antia Brademann

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without written permission from: Director-General, Environment, Planning and Sustainable Development Directorate, ACT Government, GPO Box 158, Canberra ACT 2601.

Telephone: 02 6207 1923 Website: www.environment.act.gov.au

Privacy Before making a submission to this discussion paper, please review the Environment, Planning and Sustainable Development Directorate’s privacy policy and annex at www.environment.act.gov.au/about/ privacy. Any personal information received in the course of your submission will be used only for the purposes of this community engagement process. All or part of any submissions may be published on the www.environment.act.gov.au website or in any subsequent consultation report. However, while names of organisations may be included, all individuals will be de-identified unless prior approval is gained.

Accessibility The ACT Government is committed to making its information, services, events and venues as accessible as possible.

If you have difficulty reading a standard printed document and would like to receive this publication in an alternative format, such as large print, please phone Access Canberra on 13 22 81 or email the Environment, Planning and Sustainable Development Directorate at [email protected]

If English is not your first language and you require a translating and interpreting service, please phone 13 14 50.

If you are deaf, or have a speech or hearing impairment, and need the teletypewriter service, please phone 13 36 77 and ask for Access Canberra on 13 22 81.

For speak and listen users, please phone 1300 555 727 and ask for Access Canberra on 13 22 81.

For more information on these services visit www.relayservice.com.au CONTENTS

EXECUTIVE SUMMARY 1 4 ECOLOGICAL OBJECTIVES FOR ACT AQUATIC 27

1 INTRODUCTION 5 5 ENVIRONMENTAL FLOWS FOR PARTICULAR 1.1 Background 5 ECOSYSTEMS 33 1.2 Purpose of the guidelines 6 5.1 Water supply ecosystems 38 1.3 National responsibilities 6 5.2 Natural ecosystems 42 1.4 Statutory basis for environmental flows 5.3 Modified ecosystems 43 in the ACT 8 5.4 Urban ecosystems 46 1.5Review of the guidelines 9

6 MONITORING AND ASSESSMENT 49 2 DETERMINATION OF ENVIRONMENTAL FLOWS 11 6.1 Applying the framework to the different 2.1 Basis for determination of environmental flows11 ecosystems and flow components 50 2.2 Adaptive management 11

2.3 Economic and social issues 12 GLOSSARY AND BIBLIOGRAPHY 53 2.4 Water quality issues 12

2.5 Impoundment release structures 12 APPENDICES 61 2.6 Augmentation of stream flows 13 Appendix 1: Scientific Basis For Recommendations 2.7 Climate change 13 From 2004 Review Of The Environmental 2.8 15 Flow Guidelines (1999) 61 2.9 Upstream influences 16 Appendix 2: Recommendations From 2010 2.10 Types of ecosystems 16 Review Of The Environmental Flow Guidelines (2006) 64 Appendix 3: 3 ENVIRONMENTAL FLOW APPROACH Scientific Basis For Recommendations ADOPTED 19 From 2017 Review Of The Environmental 3.1 Techniques for calculation of flows 20 Flow Guidelines (2013) 65 3.2 Components of environmental flows 21

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES c d DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES EXECUTIVE SUMMARY

The Environmental Flow Guidelines are an instrument under the Water Resources Act 2007 that set out the flow requirements needed to maintain aquatic ecosystems. The Guidelines have been developed using the most up to date scientific information available, and will be used with Water Resource Management regulatory instruments under the Water Resources Act 2007, water available from areas determination and Water Management Areas determination to manage ACT water resources.

Environmental flows, for the purposes of the Water Resources Act 2007, are specified in Table 3 of Section 5 for each category and each specific reach. The Environmental Flow Guidelines apply to all , streams, lakes and in the ACT. The 2018 Environmental Flow Guidelines replace the 2013 Environmental Flow Guidelines.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 1 PURPOSE OF ENVIRONMENTAL FLOWS Environmental flows describe the quantity and timing The base flow is the flow component contributed of water required to sustain freshwater ecosystems. mostly by groundwater, and is the minimal volume of water that the stream needs to support the , We rely on our waterways for a range of functions plants, insects, and protect water quality. The volume including and conservation, irrigation of the base flow is determined for each month for each and domestic water supply. Waterways need to be stretch of stream or . healthy to provide these functions. The natural flows in ACT streams are highly variable. Rivers and streams The purpose of the small and larger floods, termed naturally have periods of both very low and very riffle, pool, and channel maintenance flows, is to move high flows. Flows in our streams also vary seasonally out sediment deposits and maintain channel form. with the higher flows usually occurring in the spring The movement of sediment is important for months. The Environmental Flow Guidelines identifies maintaining healthy aquatic ecosystems. Riffles are those components of flow from this variable flow the shallow fast flowing sections of the river. The regime necessary to maintain stream health. One way riffle maintenance flows scour out fine sediment that to do this is to specify environmental flows that mimic accumulates in riffles, damaging these habitats for the flows that would occur naturally. In more heavily fish, water plants and other aquatic life. The pool and used systems such as water supply catchments it may channel maintenance flows scour sediment from pools be necessary to protect specific components of the and ensure the river maintains its natural channel form. flow regime to keep aquatic ecosystems healthy. Special purpose flows are flows designed for a In highly modified ecosystems, the environmental particular ecological need, for example the flow flows needed to ensure critical processes occur and needed to encourage breeding of a species of fish, or provide habitat, may be very different to the natural to protect habitat of a frog species. The Guidelines flow regime that occurred before development. make provision for special purpose flows should they be identified. However no special purpose flows are currently specified in the Guidelines. COMPONENTS OF ENVIRONMENTAL FLOWS Impoundment drawdown levels are the levels that a reservoir, lake or needs to be kept within, so that To account for natural variability, the Environmental impacts on macrophytes, sediment processes and Flow Guidelines include protection of particular water quality do not result in adverse changes to the components of the natural flow. These are: state of the ecosystem. Static impoundment levels can >> base flow; result in a limited fragile ecosystem dominated by a few species of flora and fauna even though the >> small floods (riffle maintenance flows); can be high. Excessive fluctuations in impoundment >> larger floods (pool or channel maintenance flows); levels can result in a denuded barren water body that >> special purpose flows; and supports little biomass and low biodiversity. >> impoundment drawdown level.

2 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES >> HOW ENVIRONMENTAL FLOWS Flows specified for these catchments are the minimal ARE PROVIDED requirement for healthy aquatic ecosystems, while ensuring that both water supply and conservation In the ACT environmental flows are provided in one of objectives can be met. This approach is appropriate two ways: either by releases or spills from dams, or by for these catchments as the intensive monitoring of the restricting the volume of water that can be abstracted system allows adaptive management to be implemented from a water management area. In the ACT the volume if adverse effects are detected. of water available for abstraction within each water Special rules for drought periods have also been specified management area is limited to the volume remaining for these catchments. The Guidelines recognise that after environmental flow volumes have been provided. during dry times when the urban population faces water Abstraction rules are also applied to ensure that licensed restrictions, it is appropriate that environmental flows abstractors do not impact on waterways during critical also be reduced. flow events such as very low flows, flooding flows or cause excessive drawdown levels. The ACT only abstracts up to about 10% of available flows on average, with the remaining 90% effectively environmental flows. In ENVIRONMENTAL FLOWS IN URBAN PURPOSE OF addition, only the water supply dams significantly modify CATCHMENTS ENVIRONMENTAL FLOWS flows in downstream river reaches. Urbanisation has caused considerable modification to the streams flowing through urban areas. The increase in Environmental flows describe the quantity and timing impervious surfaces, including roads, roofs and car parks, of water required to sustain freshwater ecosystems. ECOLOGICAL OBJECTIVES FOR has caused a higher rate of runoff than occurred naturally. We rely on our waterways for a range of functions ENVIRONMENTAL FLOWS In addition urban watering has led to many urban streams including biodiversity and conservation, irrigation now having unnatural permanent flow. Increased flows in and domestic water supply. Waterways need to be Setting ecological objectives for waterways allows urban streams can stress aquatic ecosystems. For urban healthy to provide these functions. The natural flows specific ecological values to be protected by streams, the Guidelines identify the natural baseflow in ACT streams are highly variable. Rivers and streams components of the environmental flow regime. In and channel maintenance flow that should be protected, naturally have periods of both very low and very addition, ecological objectives can be used to assess and recommends that the additional runoff from urban high flows. Flows in our streams also vary seasonally the effectiveness of environmental flows, and the development be made available for abstraction. This serves with the higher flows usually occurring in the spring information used to refine the Guidelines. the dual purpose of protecting streams from the effects of months. The Environmental Flow Guidelines identifies The ecological objectives and indicators of these frequent short duration high flows, and allows greater use of those components of flow from this variable flow objectives identified in the Guidelines are based on second-class water in the urban area. regime necessary to maintain stream health. One way the Territory Plan, ACT legislation, Commonwealth to do this is to specify environmental flows that mimic threatened species legislation, ACT Government policies the flows that would occur naturally. In more heavily and knowledge gained from research. As an example, an ENVIRONMENTAL FLOWS IN OTHER used systems such as water supply catchments it may ecological objective for the reach between CATCHMENTS be necessary to protect specific components of the and Cotter Reservoir is to maintain Environmental flow requirements are also set for streams flow regime to keep aquatic ecosystems healthy. populations of the endangered fish species Macquarie in natural ecosystems, such as those within Namadgi In highly modified ecosystems, the environmental Perch. An indicator of success in meeting this objective is National Park and Tidbinbilla Nature Reserve, and in flows needed to ensure critical processes occur and that recruitment of Macquarie Perch is detected at greater modified ecosystems in rural ACT. The Guidelines for provide habitat, may be very different to the natural than 75% of monitoring sites in the reach. flow regime that occurred before development. these systems are designed to protect the base flow and also protect most of the volume of flood flows that are necessary to maintain the channel form. In these ENVIRONMENTAL FLOWS IN catchments limiting the quantity of water that can be COMPONENTS OF WATER SUPPLY CATCHMENTS abstracted protects environmental flows. ENVIRONMENTAL FLOWS In the water supply catchments a balance between To account for natural variability, the Environmental environmental needs and consumptive needs has to be Flow Guidelines include protection of particular made in the Guidelines to ensure that there is adequate INDIGENOUS WATER - components of the natural flow. These are: supply of water for domestic consumption. At the same VALUES AND USES >> base flow; time, there is a requirement to maintain the health of the The values and uses of Indigenous water are currently >> small floods (riffle maintenance flows); rivers, and in particular to protect the two endangered being identified through the ACT Water Resource fish species that live in the Cotter River. The environmental Plan process. While Indigenous water is different to >> larger floods (pool or channel maintenance flows); flows that are recommended for the water supply environmental flows, where it relates to meeting the >> special purpose flows; and catchments are based on the extensive information about ecological objectives shown in Table 2 and supporting >> impoundment drawdown level. environmental flows in the Cotter River. the environmental flow requirements in Table 3, it will be included in future environmental flow guidelines.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 3 1 INTRODUCTION

4 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 1 INTRODUCTION

1.1 BACKGROUND Increasing demands for the allocation of water for off- stream uses has resulted in substantial changes in the streamflow regimes in many streams across Australia. These changes in streamflow have contributed to major impacts on aquatic habitats and ecology. In some Australian streams, allocation of water for off- stream uses can exceed total flow resulting in patterns of flow that reflect the rights of water users rather than the requirements of the streams and their ecological processes. Consumptive uses are often given priority, as water rights, entitlements, and licences have legal and commercial status. With the growing use of market forces as the basis of resource allocation, there is a need to ensure that environmental quality and ecological requirements are not disadvantaged. Over past decades there has been an acceptance of the need to give explicit recognition to environmental flow needs through the establishment of water specifically for the environment. Similarly, it is accepted that there is a relationship between surface and ground water and that ground water abstraction will impact on base flows of surface streams. Many aquatic ecosystems in the ACT are modified as a result of changes in land use, changes to river channels and , streamflow diversion, discharges to streams, introduction of flora and fauna, and recreational fishing. Some of these systems, particularly urban lakes and streams, categorised as urban ecosystems are highly valued in their own right. Other aquatic ecosystems are in a condition close to that prior to European settlement. Depending on the condition of a stream and the environmental values specified for that stream, the planning and management issues in respect to environmental flows vary from: >> managing streamflow diversion and discharges so as to maintain the current status of the aquatic ecosystems; to >> managing streamflow diversion and discharges so as to restore aquatic ecosystems to a standard to meet the community’s environmental values. It should be recognised that the guidelines for environmental flows in this document are based upon the best scientific knowledge available at the time they were drafted. The determination of environmental flows is an active research field and this document will be refined and amended as the knowledge base grows.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 5 1.2 PURPOSE OF THE GUIDELINES In line with the ESD precautionary principle, the ACT environmental flow guidelines are conservative These Guidelines are a statutory instrument to be used and may need to be reassessed in light of further when determining volumes in the Water Resource knowledge and experience. In water supply Plan and in the regulation of water abstraction. catchments a smaller safety margin is accepted on the Environmental flows, for the purposes of the Water basis of our better understanding of such streams, and Resources Act 2007, with respect to each ecosystem in recognition of the importance of the water supply category and specific reaches within are specified in function of these catchments. Table 3 of Section 5. The ACT is also party to the 1994 and 1995 Competition Policy and related reforms agreements. These include the COAG agreement on the strategic framework for 1.3 NATIONAL RESPONSIBILITIES the efficient and sustainable reform of the Australian The Intergovernmental Agreement on the Environment water industry. Amongst other things, this requires the (1992) sets out clear guidance on land use decision setting of environmental flow requirements based on and approval processes to ensure development is the best available scientific advice. The 2004 National ecologically sustainable. The National Strategy for Water Initiative confirms this requirement. Ecologically Sustainable Development (1992) sets the As a signatory to an intergovernmental agreement goal of Ecologically Sustainable Development (ESD) established under the Murray-Darling Basin Plan as ‘development that improves the total quality of life, (the Basin Plan), the ACT is required to manage both now and in the future, in a way that maintains water resources in a way that is consistent with the the ecological processes on which life depends’. requirements of the Basin Plan. The establishment of When applied to ecosystems this core objective is Basin Plan in 2012, under the Commonwealth Water Act expressed as ‘protection of biological diversity and 2007, was a major change to the way in which water is the maintenance of essential ecological processes managed across the Murray-Darling Basin. and life support systems’. These guidelines have been prepared with these principles in mind.

6 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES With respect to fish, the BWS identifies the following requirements: >> Increase populations of Macquarie Perch in at least 2 of 6 sites, one of which is the Cotter River (Table 8 and the Cotter River is also a site of significance in Appendix 7); >> Increase populations of Silver Perch in at least 1.2 PURPOSE OF THE GUIDELINES As a signatory, the ACT is required to develop a 10 year Water Resource Plan (WRP). The WRP is required to 2 of 7 sites, one of which is in reaches of the These Guidelines are a statutory instrument to be used set out the amount of water that is available for the (Table 8); when determining volumes in the Water Resource environment and the rules and arrangements for using >> Expected outcomes for native fish (pp45 to 46) Plan and in the regulation of water abstraction. that water, ensuring consistency with the Basin-wide Noting that these BWS outcomes are reliant on other Environmental flows, for the purposes of the Water environmental watering strategy (BWS, MDBA, 2014a). factors such as land management, and not just by Resources Act 2007, with respect to each ecosystem Thus, the revised EFG will be central to the ACT’s WRP environmental flows. category and specific reaches within are specified in and have been prepared with these requirements in Table 3 of Section 5. mind. The Basin Plan also requires that Priority Environmental Assets (PEAs) and Priority Ecological Meeting the ACT’s obligations necessitates Functions (PEFs) are identified in the ACT Long Term consideration of Basin Plan requirements and Watering Plan, required by the Basin Plan sections 1.3 NATIONAL RESPONSIBILITIES incorporation of the environmental outcomes 8.18 to 8.22. The methods for formally identifying The Intergovernmental Agreement on the Environment expected by the BWS. The Basin Plan sets out three PEAs, PEFs and their environmental watering (1992) sets out clear guidance on land use decision broad environmental objectives for water-dependent requirements are detailed in the Basin Plan (Chapter and approval processes to ensure development is ecosystems (section 8.04): 8, Part 5; reproduced in Appendix 6). Fundamental to ecologically sustainable. The National Strategy for 1. Protect and restore water-dependent ecosystems identifying the PEAs and PEFs in the ACT Long Term Ecologically Sustainable Development (1992) sets the 2. Protect and restore the ecosystem functions of Watering Plan is that they are environmental assets or goal of Ecologically Sustainable Development (ESD) water-dependent ecosystems functions that can be managed with environmental as ‘development that improves the total quality of life, water. Many of the ACT’s important freshwater assets both now and in the future, in a way that maintains 3. Ensure that water-dependent ecosystems are are located in conservation areas and cannot be the ecological processes on which life depends’. resilient to climate change and other risks and managed with environmental water, beyond limiting When applied to ecosystems this core objective is threats. extractions. For example, the Ginini Flats expressed as ‘protection of biological diversity and The BWS expands on these objectives by detailing Ramsar site is located in the headwaters of Ginini the maintenance of essential ecological processes expected outcomes for four ecological components Creek in Namadgi National Park. Water cannot be and life support systems’. These guidelines have been of water-dependent ecosystems: river flows and delivered to this asset, the way of managing water at prepared with these principles in mind. connectivity, native vegetation, waterbirds and native fish. this site is by preventing extraction.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 7 1.4 STATUTORY BASIS FOR land and water uses which impact on the sustainability of identified environmental or water use values. ENVIRONMENTAL FLOWS It is therefore necessary that appropriate flows be IN THE ACT provided to protect the environmental and use values of ACT waterbodies. Water Resources Act The Territory Plan explicitly requires that The preparation of environmental flow guidelines is a environmental flows be maintained to ensure that requirement of the Water Resources Act 2007. This Act the stream flow and quality of discharges from has the objectives of: all catchments protect environmental values of >> ensuring the use and management of water downstream waters. Four policies are elaborated to resources to sustain the physical, economic and achieve this objective: social wellbeing of the people of the Territory, while >> land use and management practice shall be protecting the ecosystems that depend on those cognisant of streamflow and water quality impacts resources; downstream; >> protection of waterways and aquifers from damage >> stream-flow diversions shall be restricted to and, where possible, to reverse damage that has authorised diversions; already occurred; and >> lake and reservoir releases shall be consistent with >> ensuring that water resources are able to meet the the protection of downstream ecology and water reasonably foreseeable needs of future generations. uses; and To achieve these objectives the Water Resources >> groundwater abstraction shall be consistent with Act 2007 (The Act) requires that Environmental Flow authorised abstraction. Guidelines be prepared to set out the flows necessary to maintain aquatic ecosystems in ACT waterways. Implementing these policies necessitates defining The Act also requires the determination of areas (Water quantitative environmental flow guidelines for all Management Areas) for managing the water resources streams, rivers, lakes, and aquifers in the ACT and the of the ACT and requires that the amount of water control of abstraction of the volumes not required by available for taking from each area is determined. the environment. The Act further provides that the Environment Protection Authority may license the taking of both Supporting legislation and strategies surface and groundwater from areas as provided for by The objectives of the Territory Plan and the the water available from areas determination and the Water Resources Act 2007 are supported and Environmental Flow Guidelines. complemented by the provisions and strategies contained in the Environment Protection Act Territory Plan 1997, the Nature Conservation Act 2014 and the Implementation of the Water Resources Act 2007 needs ACT Nature Conservation Strategy 2013-23. The to be consistent with the Territory Plan. Three types Environment Protection Act 1997 provides support of water use catchments are identified in the Territory by the enforcement of water quality and chemical Plan (Section 11.8 Water use and catchment general use standards. The Nature Conservation Act and code); ‘conservation’, ‘water supply’, and ‘drainage and ACT Nature Conservation Strategy support the open space’. These uses have been designated as the conservation of native species, communities and primary uses for the waterbodies within these types of habitats essential to the protection of the wellbeing of catchment. aquatic habitats. Within each of these catchments, secondary use The Environmental Flow Guidelines will also values are also specified and include provision of be complemented by Action Plan 29, ‘Ribbons recreational amenity, supply of potable or second of Life’ the Aquatic Species and class water, provision of aquatic habitat, and Conservation Strategy or the ACT Aquatic and remediation of low quality urban stormwater (Section Riparian Conservation, Strategy and Action Plans, 11.8 of the Plan). Where several secondary uses are when finalised. The Strategy guides conservation and specified for a water body, that water body is to be recovery of aquatic and riparian species in natural managed to achieve the use with the most stringent water systems. requirements, so that other uses are not compromised by relaxation of standards. National waters Under the general principles and policies, the Territory These Guidelines include environmental flows for the Plan requires that planning be guided by the principles downstream of and of ecological sustainability and exclude catchment drawdown limits for .

8 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Lake Burley Griffin remains under the control of the Part 8 Division 2 specifies the flow at which take can Commonwealth and is managed by the National commence, which is approximately equal to the 95th Capital Authority. Environmental flows for Lake Burley percentile for the Murrumbidgee and Queanbeyan Griffin are recommended given the ACT’s responsibility Rivers and the 80th percentile for the Molonglo River. To to protect ACT water resources upstream of Lake ensure protection of the Commonwealth’s paramount Burley Griffin including the Jerrabomberra Wetlands rights to these waters under the Seat of Government and the Molonglo River, as well as the Molonglo River Acceptance Act 1909 for the purposes of the Territory, downstream of Lake Burley Griffin. The National Capital it is expected that water use be limited to that Authority recognised the need for environmental flows necessary to support stock and domestic purposes from Scrivener Dam in their management practices. for traditional grazing enterprises and associated long The Guidelines therefore specify environmental flows established rural villages (or equivalent use). Part 5 for all waterways lying within the ACT. Following Division 2 of the NSW water sharing plan specifies the enacting of Commonwealth legislation Access the flows available for stock and domestic rights in Canberra is responsible for administering the provision the relevant catchments. This is expected to ensure and allocation of water entitlements and licences for that adequate environmental flows into the ACT are the waters of Lake Burley Griffin. Lake Burley Griffin maintained. Note also that there are currently no water also has its own management plan administered by the requirements for native title rights in this NSW water National Capital Authority. sharing plan. Paramount rights to Queanbeyan and In this context, these guidelines only specify the Molonglo waters environmental flows in NSW immediately downstream of as these flows are under the direct By the Agreement between the Commonwealth and control of the ACT through regulation of releases. NSW for the surrender of territory by NSW for the Seat of Government, the Commonwealth gained The ACT ensures that environmental flow paramount rights to the waters of the Queanbeyan requirements in the rivers it has responsibility for are and Molonglo Rivers and their tributaries (in NSW) for met by flows under the control of the ACT, principally all the purposes of the Territory (Seat of Government water running off ACT land. Acceptance Act 1909). The Commonwealth has developed the waters of the for the purposes of urban water supply for the ACT through 1.5REVIEW OF THE GUIDELINES the construction of the Googong Dam. Through the Commonwealth Canberra Water Supply (Googong Actual flows and their effect on stream structure and Dam) Act 1974, the Territory Executive exercises the ecology will be the subject of an ongoing monitoring rights to the waters of the Googong Dam Area and this and evaluation program. Recommendations for includes any necessary releases from the Googong monitoring and evaluation are provided in Section Dam. The Canberra Water Supply (Googong Dam) Act 6 Monitoring and Assessment. The program will be 1974 also requires that environmental needs be taken used to evaluate the effectiveness of the Guidelines. into account in water resources management. The first guidelines were published in 1999 and were reviewed after 5 years. The changes to the While the only NSW waters yet developed for ACT urban original guidelines focussed mainly on the setting water supply are those entering Googong Reservoir, the of environmental objectives and adjustments to the remaining waters over which the Commonwealth has flows in water supply catchments. Changes to the 2006 paramount rights (that is, the Molonglo River upstream Guidelines provided a framework for accommodating of the ACT and upstream of the climate change and aspects relating to updated water ACT) are important for other ACT purposes, including supply infrastructure. Further recommendations the protection of aquatic ecosystems in the ACT. from reviews conducted in 2010 and 2017 have been Without appropriate environmental flows entering incorporated into the Guidelines. The scientific basis the ACT from the Molonglo River and Jerrabomberra for these recommendations and amendments has Creek the ACT may not be able to ensure appropriate been appended to the Guidelines environmental flows in these waterways in the ACT and further downstream in NSW. The determination The Guidelines will be reviewed after a further five and maintenance of flow requirements in these waters years of operation to determine if the ecological to protect environmental values is the responsibility objectives specified are the most appropriate, and of NSW. The current NSW rules for taking water from the environmental flows required achieve those river reaches upstream and downstream of the ACT objectives. The review may be conducted earlier if are contained in the “Water sharing plan for the evidence indicates it is warranted. Murrumbidgee unregulated and alluvial water sources 2012”.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 9 2 DETERMINATION OF ENVIRONMENTAL FLOWS

10 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 2 DETERMINATION OF ENVIRONMENTAL FLOWS

2.1 BASIS FOR DETERMINATION OF ENVIRONMENTAL FLOWS The concept of environmental flow is based on the recognition that aquatic ecosystems are adapted to natural flow conditions and modification of the flow regime will impact on the ecosystem. Additionally, the geomorphological structure of streams is largely determined by the flow regime, with flow-on effects on stream biota through changes to substrate type and available habitat. Flow regime refers not only to the quantity of water but also to the variability of flow and incidence of flood and low flow events. For long term viability of some ecosystems there may be a need for periods of low flow. In practice it may be difficult to determine the effect of an ‘environmental flow’ component in isolation from other factors such as water quality. The environmental flows have been determined by relating the Territory Plan requirements to protect specific aquatic ecosystems with the scientific basis for sustaining significant ecosystems or species.

2.2 ADAPTIVE MANAGEMENT Adaptive management is the systematic process of continually improving management policies and practices by learning from the outcomes of an experimental approach to operational programs (Peat et al. 2017). The principles of adaptive management have been embedded in the ACT’s Environmental Flow Guidelines, with environmental flows management integrated with ecological objectives, monitoring and reporting requirements. The flow regimes specified within the Environmental Flow Guidelines have been developed within an adaptive management cycle (Peat, 2007), with investment in monitoring, assessment and research to fill knowledge gaps. The focus has been on balancing the needs of the water users with the requirements of the freshwater ecosystems and has resulted in the refinement of the defined flow requirements and recommended flow regimes. Strategies for further improving environmental flow implementation within an adaptive management framework include the regular production and review of monitoring reports as part of a documented process. Information from monitoring reports and other experimental flow releases can then be used as the basis for making informed flow management decisions.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 11 2.3 ECONOMIC AND SOCIAL if water is released from the lower layers of deep, stratified reservoirs where the water can have a ISSUES much lower temperature and oxygen content than The primary purpose of Environmental Flows is to surface waters. If this bottom water is released to maintain aquatic ecosystems, however, the social, and meet environmental flow requirements, its quality economic consequences of the Environmental Flow may compromise its value for the maintenance of Guidelines are also taken into account through two aquatic ecosystems. For example, many native fish approaches. First, the Guidelines recognise that there species use water temperature, day length and flow as are different social and economic factors associated cues for reproduction, and the temperature of water with the three types of water use catchments released to meet an environmental flow requirement identified in the Territory Plan: may severely disrupt spawning, migrations, and >> Conservation; reproductive activity. In catchments where reservoir releases are made to meet environmental flow >> Water Supply; and requirements, the water quality of the release is to >> Drainage and Open Space. match as closely as possible to that of the water flowing into the reservoir. The Territory Plan policies for these catchments identify different social and economic values and Water Quality is covered in the Environment Protection priorities for these catchments. The Guidelines take Act 1997 and the Territory Plan Water Use and account of these priorities in setting environmental Catchment General Code (Planning and Development flow requirements. For example, in Water Supply Act 2007). catchments, the primary value is domestic water supply, and in recognition of this a smaller margin for protection of aquatic ecosystems has been adopted 2.5 IMPOUNDMENT RELEASE to provide greater volumes of water for domestic STRUCTURES supply. In Conservation catchments, the priority is on protection of natural resources and conservative Most of the dams in the ACT were built before the environmental flow guidelines have been set with importance of environmental flows was identified those values in mind. These Guidelines recognise that and may not be best suited to meet the operational the economic and social importance of water can requirements of the environmental flows specified vary over time, particularly during periods of drought. in these guidelines. In particular, this relates to the The Guidelines accommodate this factor by changes temperature and flow variations to mimic natural to the environmental flow requirements during times conditions. Ideally, the water released from a of drought, balanced against the continuing need to reservoir for environmental purposes should match also protect aquatic ecosystems during such critical as closely as possible the temperature of the water periods. entering the reservoir or lake. The major water storage structures; Corin, Bendora, Cotter and Provision of environmental flows and protection Googong Dams all have the capacity to release water of aquatic ecosystems and threatened species is a from a variety of depths and so inflow and release requirement under both ACT and national legislation, water temperature can be matched. In practice, the and is an obligation under national agreements to depth from which water is drawn for environmental which the ACT is a party. Given these fundamental flow releases is often determined by the quality obligations, the social and economic issues identified requirements for water supply, which are not always through public submissions received during the the same as the temperature requirements to protect consultation process and workshops with relevant downstream aquatic ecosystems. The current subject experts, have been taken into account in adaptive management process will continue to ensure developing the Guidelines. that infrastructure will be managed to, as closely as possible, meet the Guidelines. The Guidelines do not require environmental flow 2.4 WATER QUALITY ISSUES releases from ACT urban lakes and ponds. These Both water quality and water quantity characteristics waterbodies only have the capacity to release water by have effects on ecosystems, and in some areas overtopping, or discharge through a valve at the base these are strongly interrelated. Although these of the dam. Water in the bottom of these reservoirs environmental flow guidelines focus on water quantity is often of low quality and the release of this water and flow regimes, water quality issues factor in the would potentially compromise downstream aquatic discussions. For example, water quality problems may ecosystems. However, any reductions in streamflow arise when water is released from impoundments to downstream and caused by the urban dams tend meet downstream environmental flow requirements to have been compensated by the increased runoff

12 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES from the urbanised area. Consequently, the flows in Discharge of treated wastewater is the other process urban streams downstream of impoundments in the that significantly augments river flows. The ACT ACT, generally have been at or above the specified through the diverts up to 50 GL a year for baseflow (the 80th percentile flow), see Figure 7 (Dusting urban water supply. Of the amount diverted, around et al, 2017). The urban dams are sized relative to their 60% is returned to streams as treated effluent. catchment for purposes of attenuating storm peaks Downstream of the Queanbeyan and Lower Molonglo and improving water quality and are full for the most sewage treatment works on the Molonglo River there of the time. Medium flow events and large floods is a significant increase in base flows as a result of entering the lake pass through and on down the river. the return of treated effluent to the river. Augmented Flows downstream of the lakes are also augmented by flows are not necessarily of benefit to the aquatic increased flows from downstream urbanised tributaries. ecosystems because natural ecosystems are not adapted to the constant, high base flows that large Similarly, Scrivener Dam on the Molonglo River, sewage treatment plants can discharge. In addition, managed by the Commonwealth, currently does contaminants such as nutrients and salt in the not have a multi-level off-take. Releases can only be discharged effluent from sewage treatment plants may made through a valve at the base of the dam, or by compromise the value of the returned flows to rivers. opening the dam gates. Under the Commonwealth ACT Water Management Legislation Amendment Act Where streamflow is unnaturally augmented either by 2013 management of take of Commonwealth water stormwater runoff or by sewage treatment discharge, resources (including Lake Burley Griffin) in the ACT has reuse is encouraged within limits, for example, within passed to the ACT Government. The National Capital the sustainable abstraction limit for a sub-catchment, Authority and the ACT Government will together so that stream flows more closely approximate those formulate how to meet environmental flow obligations prior to urbanisation. Streamflow augmented by water for the ACT and under the Basin Plan, both in Lake transfers should be managed in a manner to minimise Burley Griffin and in the Molonglo River downstream, adverse effects and maintain the values of the stream. while ensuring that Lake Burley Griffin fulfils its functions amenity functions for central Canberra. This includes consideration of reviewing operational 2.7 CLIMATE CHANGE flexibility to allow releases and assist in meeting other ecological objectives. The water resources of southern and eastern Australia are identified as one of our national resources most vulnerable to climate change (Bates 2010). The impacts 2.6 AUGMENTATION OF STREAM of projected climate change in the coming decades are expected to alter the hydrology of ACT streams, FLOWS which in turn may result in fundamental changes in Streamflow in the ACT is augmented through various the stream ecosystems regardless of whether they be processes that include urban runoff, water transfers in a ‘pristine’ state or modified by human intervention. and return of treated wastewater to streams, which These climate change projections are likely to affect need to be managed to avoid detrimental changes to water-dependent ecosystems in a range of ways, aquatic ecosystems. but most directly through changes to temperature and water availability (Prober et al. 2015, Dyer et In urban areas, the increased stormwater runoff from al. 2013). Other possible consequences include: roofs and roads can increase flow volume unnaturally insufficient water to support fish spawning during and change flow variability, particularly in small crucial reproductive windows; reduced connectivity streams. Urban runoff can also degrade streams if the in streams, limiting the dispersal ability of plants and water is of a poor quality. At the same time, it should animals; reduced connectivity through the riparian be recognised that the community values some urban zone as drier conditions reduce vegetation condition, streams that now flow permanently in contrast to their and potentially facilitate weed invasion (Lavergne prior ephemeral but natural condition. et al. 2010, Morrongieelo and Balcombe, 2011; ACT Streams can be used to transfer water between water Government 2016). Human needs may also change storages. ACT examples of this are the reach between in combination with potential demographic and Corin and Bendora Reservoirs on the Cotter River and land-use changes, which may in turn alter the human a section of Burra Creek that will be used as a conduit impact on the ACT’s natural water resources. In sum, for water abstracted from the Murrumbidgee River for these changes may affect the efficacy of the current storage in Googong Reservoir. Higher more constant environmental flow program and/or the adequacy of flows than natural can alter ecosystem processes and the current monitoring program. change stream geomorphology.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 13 The ACT’s Biodiversity Adaptation Pathways Project Reference sites assessed by AUSRIVAS should be Band It would be sensible to continue the current AUSRIVAS report discusses e-flows including deliberate release A with impacted sites usually being Bands B, C or D. It is program while paying particular attention to the of cold water to manage climate change effects, in reasonable to expect that climate change will affect both performance of reference sites. To improve the regards to “improve cross-border implementation of reference and impacted sites – possibly differentially sensitivity of this approach further reference sites environmental flows” and “identify, establish, manage – which may result in changes to the ‘achievability’ of might be added to the monitoring program. and protect refugia (including use of cold water dam ecological objectives and the measurement of progress If however, extreme climate change effects occur and releases)” and “rehabilitate and expand (cold water) towards achieving them. A significant response to ecosystems were to decline over time, as drought fish habitat and enhance in-stream connectivity”. climate change at reference sites may result in their and other impacts overcome their resilience, and having a biological condition outside of Band A. To The work of Dyer et al. (2013) suggests that changes particularly if Natural Ecosystems decline (e.g. their identify such change, it would be essential to monitor a in temperature are likely to have far greater effect on macroinvertebrate communities consistently in ‘sub-A’ sub-set of reference sites used in building the AUSRIVAS aquatic biota (macroinvertebrates and native fish) AUSRIVAS band), a more fundamental revision of the predictive models. If a shift in the reference condition than changes to flow regimes. However, there remains objectives within the Guidelines is called for. It may be was observed management may: uncertainty around the specific effects of climate necessary to review the type of aquatic ecosystems we change on a reach-to-reach scale in the ACT. The holistic 1. Accept the altered condition of the ‘reference’ sites are aiming to support/reinstate through environmental approach adopted in the Environmental Flow Guidelines as the new reference condition and adjust the flow management as well as developing new (see Section 3) is one of ensuring maintenance of good Ecological Objectives (indicator values) accordingly. arrangements that share the significantly depleted catchment condition, with the principle of assisting 2. Resample the reference sites and modify the resource. This is an extreme response and need be adaptation to a changing climate by promoting predictive models to reflect the post-climate changed considered only if the monitoring results show it is ecosystem resilience. This ‘whole of landscape’ situation and retain the current indicator values. necessary. approach focused on ecosystem resilience is consistent The identification of climate change issue for fish with the ACT Nature Conservation Strategy 2013-2023 and The second option is probably preferable because performance indicators is another task for the next 5 ACT Climate Change Adaptation Strategy and provides it acknowledges the reality of climate change but years. a best practise approach to managing freshwater uncouples the flow management response from the ecosystems in an uncertain and changing climate. response to climate change. It is important to note that there is no need for any of these responses (or to Climate change effects need to be considered for the choose a response) unless and until the reference sites 2.8 GROUNDWATER ongoing monitoring of aquatic ecosystems. Many of score is consistently outside Band A. This is unlikely in the indicators chosen to reflect the achievement of the medium future under moderate climate change Aquifers in the ACT fall into two types, aquifers in ecological objectives (the performance variables) are considering that: fractured rock and aquifers in alluvium. Both types of aquifers are relatively shallow and groundwater based on comparing specific biological observations >> The sub-set of reference sites currently sampled eventually discharges into lower sections of the with the same biological parameters under conditions have remained at or near Band A throughout the catchment’s waterways. Both aquifer types can of zero human hydrological impact – often referred to as recent drought; “reference condition”. Reference condition can either be support unique groundwater ecosystems however, observed, by including control sites from pristine streams >> The main monitoring indicator (AUSRIVAS at present the ecosystems in the ACT that are (e.g. Natural Ecosystems) in the monitoring program, or macroinvertebrates) operates at Family level which recognised as being groundwater dependant are small modelled using best available information and may be may mask subtle changes in the macroinvertebrate unregulated streams whose baseflow is primarily useful for elucidating climate change impacts. . assemblage; and supplied by localised groundwater discharge. >> A change of around 9% of total stream flow is not The AUStralian RIVer Assessment System (AUSRIVAS) Aquifers in alluvium generally have a more direct likely to invoke a significant change in AUSRIVAS using macroinvertebrates uses reference condition and rapid connection with surface waters whereas scores unless it is expressed in substantial changes concept to compare natural to human impacted river with fractured rock aquifers the connection between to some specific aspect of flow (e.g. seasonal reaches, but would require consideration for climate surface and groundwater may be less direct. pattern, base flow, duration of particular events). change impacts.

14 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES It would be sensible to continue the current AUSRIVAS In general, discharge from fractured rock aquifers will program while paying particular attention to the occur at the lower parts of the landscape, and the performance of reference sites. To improve the lower reaches of streams in a subcatchment will be the sensitivity of this approach further reference sites ultimate destination for the groundwater flow. Virtually might be added to the monitoring program. all water that infiltrates to the groundwater system exits into the streams. Existing work on aquifers in the ACT If however, extreme climate change effects occur and suggest they are relatively shallow, their boundaries ecosystems were to decline over time, as drought are expected to largely match the topography of the and other impacts overcome their resilience, and catchments that overlie them, and there is unlikely to particularly if Natural Ecosystems decline (e.g. their be groundwater flow between catchments. Aquifers macroinvertebrate communities consistently in ‘sub-A’ have low storage and so provide little buffering AUSRIVAS band), a more fundamental revision of the capacity against a sequence of years with low objectives within the Guidelines is called for. It may be . The extraction of groundwater necessary to review the type of aquatic ecosystems we in wet years will have an influence on baseflow in are aiming to support/reinstate through environmental succeeding dry years. Abstraction of groundwater from flow management as well as developing new both types of aquifers will ultimately affect surface arrangements that share the significantly depleted water flows in streams. Consequently, the importance resource. This is an extreme response and need be of joint consideration of surface and groundwater for considered only if the monitoring results show it is water management policies in the ACT is clear. necessary. The proportion of flow in the stream contributed by The identification of climate change issue for fish groundwater (baseflow), depends on the position in performance indicators is another task for the next 5 the catchment, and varies according to catchment years. characteristics. The baseflow contribution to streams also varies throughout the year, with baseflow contribution greater during winter and spring. This is a 2.8 GROUNDWATER consequence of reduced evapotranspiration in winter and spring and reduced summer recharge. During Aquifers in the ACT fall into two types, aquifers in summer when soil crusts tend to be hydrophobic, fractured rock and aquifers in alluvium. Both types higher rainfall intensities generate larger amounts of of aquifers are relatively shallow and groundwater surface water runoff and less groundwater recharge. eventually discharges into lower sections of the Additionally, in dry years stream flow will tend to be catchment’s waterways. Both aquifer types can dominated by baseflow. In the urban environment the support unique groundwater ecosystems however, baseflow is supplemented by drainage from garden at present the ecosystems in the ACT that are watering and other activities. recognised as being groundwater dependant are small unregulated streams whose baseflow is primarily As groundwater in both types of aquifers eventually supplied by localised groundwater discharge. discharges to streams, these Guidelines limit groundwater abstraction to ensure that there is no Aquifers in alluvium generally have a more direct impact from groundwater abstractions on in-stream and rapid connection with surface waters whereas aquatic ecosystems. with fractured rock aquifers the connection between surface and groundwater may be less direct.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 15 If groundwater abstractions are too high, the baseflow 2.10 TYPES OF ECOSYSTEMS in streams will be significantly reduced. Although in-stream aquatic ecosystems are currently adapted There have been extensive changes to land use in to natural low flow and no flow periods, there is a some parts of the ACT resulting in substantial changes high risk they will be negatively affected by ‘extended’ to stream flow and hence ecosystems. Restoration of no flow periods. It is assumed that the groundwater natural aquatic ecosystems is generally not practical. In abstraction limits would also protect other types recognition of this situation, aquatic ecosystems have of groundwater dependent ecosystems (such as been categorised into four broad types, in order to clarify wetlands, floodplains or aquifer and cave ecosystems). differences in management goals and techniques that can be used to arrive at these goals (Table 1). These All groundwater referred to in these guidelines is from ecosystems are based on the water use catchments shallow aquifers, as is all take. There is no known identified in the Territory Plan. significant connection to the Lachlan Fold Belt aquifer which underlies the ACT as well as a large area of Different environmental flow requirements have been regional NSW. set for each of the types of ecosystem referred to in Table 1; natural, water supply, modified, and urban. These requirements are discussed in detail in Section 2.9 UPSTREAM INFLUENCES 3. For the purpose of setting environmental flow requirements major rivers and streams are divided A limitation to the establishment and maintenance into reaches delineated by major confluences, lakes of e-flows in the ACT is Tantangara Dam on the or reservoirs. This procedure assumes that a degree of Murrumbidgee River headwaters, upstream of the ACT. homogeneity applies within reaches and acknowledges It is currently operated as a working storage reservoir that there are links between reaches of a river. for the Snowy Hydro Scheme and environmental flows in the upper Murrumbidgee River are limited, as Specific environmental flow requirements can then be specified in the Snowy Hydro licence. At the Tantangara determined for each reach. This procedure is applied Dam wall, about 99% of inflows were previously to all river reaches. diverted out of the Murrumbidgee River valley (Snowy Map 1 shows the Territory Plan catchment categories, Scientific Committee 2010), which was subsequently as well as river reaches which are considered regulated reduced to about 83% from 2011-12 onwards. Even and which have translucent flows (dam outflows which though environmental flow releases occur, the are effectively equal to inflows), from the major dams volume of water flowing through the ACT is reduced within the ACT and Googong Dam. from natural condition. The current operational arrangement for Tantangara Dam might benefit from re-examination when the Basin Plan is reviewed. MAP 1: WATER USE CATCHMENTS The current rules and limits on take for the Murrumbidgee River in the ACT ensure that the releases from Tantangara Dam that reach the ACT are most likely to fully pass through the ACT. However, the reduced flows from upstream restrict the potential benefits from more natural environmental flows in the ACT reaches of the Murrumbidgee River. These Guidelines need to be able to incorporate variation in flows and to take advantage of any possible future increase in released volumes.

16 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 2.10 TYPES OF ECOSYSTEMS There have been extensive changes to land use in some parts of the ACT resulting in substantial changes to stream flow and hence ecosystems. Restoration of natural aquatic ecosystems is generally not practical. In recognition of this situation, aquatic ecosystems have been categorised into four broad types, in order to clarify differences in management goals and techniques that can be used to arrive at these goals (Table 1). These ecosystems are based on the water use catchments identified in the Territory Plan. Different environmental flow requirements have been set for each of the types of ecosystem referred to in Table 1; natural, water supply, modified, and urban. These requirements are discussed in detail in Section 3. For the purpose of setting environmental flow requirements major rivers and streams are divided into reaches delineated by major confluences, lakes or reservoirs. This procedure assumes that a degree of homogeneity applies within reaches and acknowledges that there are links between reaches of a river. Specific environmental flow requirements can then be determined for each reach. This procedure is applied to all river reaches. TABLE 1: TYPES OF AQUATIC ECOSYSTEMS AND THEIR LOCATION Map 1 shows the Territory Plan catchment categories, Category of Aquatic Description Management Goal Waterbodies2 in this Category as well as river reaches which are considered regulated Ecosystem1 and which have translucent flows (dam outflows which Natural ecosystems Ecosystems that have Primary goal: maintain aquatic Waterbodies in Namadgi National are effectively equal to inflows), from the major dams (Conservation persisted in a relatively ecosystems in their pristine state. Park, excepting the Cotter River within the ACT and Googong Dam. catchments) pristine condition. Secondary goals: Range of functions catchment. including flow management and Waterbodies in Tidbinbilla Nature protection goals related to recreational Reserve. MAP 1: WATER USE CATCHMENTS activities.

Water supply Ecosystems in Primary goal: provide water supply. Waterbodies in the Cotter ecosystems catchments designated Secondary goals: range of functions River catchment. The Googong 3,4 (Water Supply to provide the ACT including protection of ecological Foreshore. catchments) water supply. values, protection of ecological values associated with the reservoirs, conservation and recreation

Modified ecosystems Majority of ecosystems Primary goals: range of functions All waterbodies not included in the (Conservation modified by catchment including protection of ecological other three categories. Includes the catchments, activities (land use values, recreation and conservation. Paddys, Murrumbidgee and Molonglo Drainage and Open change, discharges) or Secondary goal: provide water supply. rivers, and Lake Burley Griffin. Naas Space catchments) by changes to the flow and Gudgenby rivers downstream of regime. Namadgi National Park

Urban ecosystems Ecosystems in urban Range of functions including Waterbodies within the urban area, (Drainage and Open lakes, ponds, wetlands recreation, conservation, irrigation and excluding the Molonglo River. Space catchments and streams that have stormwater runoff. and Urban Areas) developed as a result of urbanisation 1 Both the terminology used to describe aquatic ecosystems, for environmental flow purposes, and the closest water use catchment category in the Territory Plan are provided. The ecosystems specified in the Territory Plan are in parentheses. 2 Waterbodies include all streams, rivers, lakes, ponds, reservoirs, and aquifers. 3 The Queanbeyan River within the Googong Foreshore and the Googong Foreshore are not identified as water supply catchments in the Territory Plan, but are considered water supply ecosystems for the purposes of setting environmental flow guidelines. 4 While the Naas and Gudgenby subcatchments have been identified as potential water supply catchments, they will not be used for the ACT’s water supply in the foreseeable future. Thus, they are regarded as Natural Ecosystems in Namadgi National Park, and Modified Ecosystems downstream of Namadgi National Park.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 17 3 ENVIRONMENTAL FLOW APPROACH ADOPTED

18 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 3 ENVIRONMENTAL FLOW APPROACH ADOPTED

A range of approaches has been used in Australia to establish environmental flow requirements. These include the holistic approach, the building block methodology, expert panel assessments and the habitat analysis model (reviewed by Arthington 1998). Different approaches have differing strengths and weaknesses, and information requirements. The holistic approach has a number of particular strengths: >> it recognises the natural flow regime as a guide to the flow requirements of a system; >> it takes the approach that the flow requirements of a system should be compiled from different flow components meeting different ecological objectives, and that this can be done using field methods, expert advice and using historical data; >> the approach considers the entire rather than a single selected component; and >> it recognises that detailed ecological understanding is not available for many Australian rivers, and that an adaptive management process should be used to refine flow requirements. Accordingly the holistic approach has been adopted for the setting of environmental flow guidelines in the ACT. This approach works by identifying the essential features of the flow regime, including the natural variability, seasonal variation, floods, and intermittent dry periods (See Figure 1). The influence of the flow components on the ecosystem components is identified, and when more information on flow requirements of particular ecosystem components becomes available e.g. fish spawning and specific flow volumes, it can be readily incorporated into the approach. This approach is augmented by establishment of special purpose flows directed at supporting specific ecological attributes (for example for the spawning of threatened fish) and limiting impoundment drawdown level (to protect aquatic macrophytes). This approach is akin to elements of the building block methodology of establishing environmental flow requirements (King and Tharme 1994). The combined approach of providing a general flow regime which is augmented by flows targeting specific valued ecosystem attributes ensures that PEAs and PEFs receive the environmental watering regime they require.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 19 FIGURE 1: SNAPSHOT OF FLOW ILLUSTRATING FLOW VARIABILITY AND FLOW ELEMENTS TO BE CONSIDERED IN AN ENVIRONMENTAL FLOW REGIME.

3.1 TECHNIQUES FOR From this analysis it was determined that flow records from 1975-2016 should be used to calculate flow CALCULATION OF FLOWS volumes for most reaches. The exception to this is For the purpose of these Guidelines, the following the reach downstream of Bendora Dam, which would methods shall be adopted as the basis for experience considerable reductions in required determining flows. environmental flows if the 1975-2016 time period is used, as prior to 1996, regular environmental flow Flow statistics, including percentile flows, will be releases did not occur. calculated using historical gauging data from stations with a suitable length of record. Modelling conducted For the Murrumbidgee River in the ACT, flow statistics during the 2017 review of the EFG indicated that the are calculated from gauged data taken subsequent time period used to establish flow statistics has a to the construction of the Tantangara Dam in 1960. considerable impact on calculated volumes. This is an interim approach and may be modified when significant environmental flow requirements In analysing appropriate time periods for flow volume in the Murrumbidgee upstream of the ACT are fully calculations, considerations included that: determined and implemented. >> ecological objectives have generally been met within these reaches over the past 5 years. However, Where an abstraction point or subcatchment the flows in these reaches have generally exceeded boundary is not co-located with a gauging station, the the minimum EFG requirements; flow at that point can be calculated from the gauged flow of the nearest appropriate station. A catchment >> the Basin Plan requires that the quantity and area– runoff relationship is used to calculate flow: effectiveness of the PEW is at least maintained; Flow = Flow x (A /A )0.7 >> small changes in daily flow (± 1-2 ML/day) are req gauge req gauge unlikely to result in observable changes in the Where Flowreq is flow at the required point, Flowgauge ecology of the system (Florance 2013, Dyer et al. is flow at the gauging station, Areq is the catchment 2013); and area upstream of the required point, and Agauge is the >> there is an absence of evidence that would aid in catchment area upstream of the gauging station (ACT selecting a time period. Government, 2004; and ActewAGL, 2011).

20 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Rainfall runoff modelling (Alluvium, 2017a, b) has been Low flows need to be maintained as close to used for subcatchments without gauges as the modelling natural low flow levels as possible, by the control of approach has been shown to calibrate accurately in those groundwater and surface water abstractions, and by subcatchments that have stream gauges. environmental releases. In water supply sub-catchments in both the Cotter and A critical decision in determination of environmental Queanbeyan river systems an alternative approach, flow requirements, including base flows, is the time the water balance approach developed by Icon Water, interval over which it is calculated. If a base flow has been used to determine flow at a point remote requirement were based on total yearly flow, it would from a gauging station. This approach uses data on ignore the natural seasonal variability in river flow. ACT inflow, outflow, evaporation and abstraction from flows are naturally higher in winter. Calculation of flows reservoirs to estimate what natural flow would have using a smaller time interval (i.e. a week) would better occurred in the absence of the reservoir. reflect natural variability, but would be impractical for licensing purposes. As a pragmatic compromise, the base flow component of the environmental flow 3.2 COMPONENTS OF requirement is specified on a monthly basis, calculated ENVIRONMENTAL FLOWS using daily flow data. Selection of a threshold that appropriately defines For ACT waterbodies there are particular components base flows has generated significant debate. In the that may need to be built into the environmental flow 1999 Environmental Flow Guidelines the 80th percentile regime for each river reach or lake. These components flow was accepted as the threshold of base flows are: based on approaches used in other jurisdictions. The >> base flows; 80th percentile flow is the volume that flows 80% of the >> riffle maintenance flows; time, that is, those commonly occurring (low) levels of flow. >> pool maintenance flows; >> channel maintenance flows; This threshold was considered in the review of the 1999 Guidelines by the Cooperative Research Centre >> special purpose flows; and for Freshwater Ecology (CRCFE) (Ogden et al 2004). >> impoundment drawdown levels. The CRCFE concluded that protection of low flows, as defined by the 80th percentile flow, had demonstrated Base flows benefits for fish and macroinvertebrates in the water supply catchments, and this flow, together with other Base flow describes the quantity of water that flows flow components, could maintain aquatic ecological down a waterway in those periods between rainfall values with moderate confidence. For operational events. In the ACT much of the baseflow originates purposes during this period, only 75% of the 80th from groundwater seepage into the stream. In the percentile was released on a daily basis as the base urban environment, the groundwater contribution is flow during the initial part of each month, with the augmented by drainage from garden watering and remaining volume released at the end of the month car washing. Downstream of dam walls, stream flow as a riffle and pool maintenance flow . This informal may also be augmented by leakage from the dam, and base flow regime maintained aquatic ecosystems in downstream of sewerage treatment plants, baseflows are the Cotter River, and was the basis for changing the significantly augmented by discharge of treated effluent. th guideline baseflow to 75% of the 80 percentile with Aquatic ecosystems in ACT rivers are assumed to the 2006 Guidelines. be adapted to periods of low flow or no flow. Such The Hillman review of the 2006 Guidelines gave conditions would have occurred before European further support to the 80th percentile flow giving an settlement and still occur in pristine catchments. appropriate baseflow volume. During the drought Ecological understanding indicates that natural low or various baseflows, below the 80th percentile, were no flow periods play an important role in maintaining trialled in water supply ecosystems. The monitoring ecosystems, permitting re-colonisation and and assessment of those lower baseflows indicated succession. However, the stresses introduced by low that the 80th percentile flow gives a low risk volume flow periods should not be exacerbated by unnaturally for sustaining ecological processes even though other long periods of low or no flow. Ecosystems are flow volumes could be used for similar outcomes particularly sensitive to impact when stressed by low albeit with higher risk and requiring more intensive flows and further stress will result in harmful impacts. monitoring. Therefore for these Guidelines this In addition, ecosystem recovery from low flow stress measure will be retained for the protection of the base may be impeded by other catchment stressors such as flow in non-water supply catchments. land use change or point source pollution.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 21 Given the importance of groundwater discharge in Flooding flows For these Guidelines this measure will be retained for maintaining base flows in streams, it is not possible the protection of the channel maintenance flow in non- Streamflow increases following storm events. These to solely rely on controls of surface water abstraction water supply catchments. Guidelines for protection of increases in flow are important for the maintenance to protect base flow requirements. One of the flooding flows are in Section 5. The effectiveness of the of aquatic ecosystems and channel structure. mechanisms to protect base flow in rivers and streams guidelines for flooding flows will be assessed through Flooding flows are of particular importance in streams is to limit abstractions of groundwater to 10% of the monitoring of the flows. downstream of water supply reservoirs. Water supply annual recharge. Studies have confirmed that limiting requirements can drastically change natural flow abstractions to 10% of the recharge is unlikely to affect regimes, causing damage to downstream aquatic Special purpose flows the ecology of streams (Barlow et al 2005), and causes communities and changes to stream structure. The Special purpose flows are volumes of water designed very little change to the frequency of low flow events Snowy River downstream of Jindabyne Dam is an to meet specific ecosystem requirements, for example (Evans et al 2005 and Rassam et al 2010). Conversely, example of what can happen to a river flow if flooding the inundation of a , or the drown-out of a increasing abstraction to 20% of the annual recharge flows are prevented from passing down a river. Without fish migration barrier. The ecological requirements was estimated to result in unnaturally low flows 20% flooding flows that section of the Snowy River has for special purpose flows in ACT rivers are not well of the time (Evans et al 2005) and is likely to have a degraded with pools filling with sand and the shape of understood, and no special purpose flows have been negative effect on aquatic ecosystems (Barlowet al the river being dramatically changed through growth of identified in these Guidelines. Further ecological 2005). Investigation of the ACT groundwater resources sand bars and the encroachment of riverine vegetation. research may lead to a need for special purpose and their effect on stream flows will continue. flows for such purposes, for example, as maintaining Three types of flooding flows have been identified for Baseflow releases from controlled dams: where spawning of native fish species in the Cotter River. ACT rivers and streams: baseflow is released from a dam with outlet controls, the baseflow should not be held at a constant 1. riffle maintenance flows. Impoundment drawdown levels for discharge for the month. Research and assessment of These are increases in flow necessary Urban lakes various baseflows volumes and release regimes in the to keep riffles clear of fine surficial sediment; Urban lakes are constructed water features, designed to Cotter River indicate that varying the discharge over 2. pool maintenance flows. protect downstream reaches from the effects of urban a two week period can mitigate some of the effects These are increases in flow necessary to runoff. Macrophytes in urban lakes are recognised caused by constant flows. In effect once the monthly keep pools clear of sediment.; and as an important ecological asset. Macrophyte stands volume has been determined, greater ecological 3. channel maintenance flows. are a significant component of aquatic habitat, and benefits can be obtained with fortnightly variations in These are increases in flow necessary for their destruction would affect dependent biota the rate of release of that monthly volume even though maintenance of the channel structure. and associated ecosystem processes including the total monthly volume remains the same. sedimentation, nutrient cycling and water chemistry.

22 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES In water supply subcatchments, specific releases can For these Guidelines this measure will be retained for be made to meet flooding flow requirements. The the protection of the channel maintenance flow in non- CRCFE recommended during the 2004 review that riffle water supply catchments. Guidelines for protection of and pool maintenance flows were required to sustain flooding flows are in Section 5. The effectiveness of the ecological values. In other ACT subcatchments without guidelines for flooding flows will be assessed through reservoirs, there is not the opportunity to meet flooding monitoring of the flows. flow requirements through specific releases. The approach taken has been to place a limit on abstraction Special purpose flows of the volume of water passing down the river in higher Special purpose flows are volumes of water designed flows to ensure that when high volume flows occur, rivers to meet specific ecosystem requirements, for example and streams will receive appropriate flooding flows. the inundation of a wetland, or the drown-out of a In order to ensure that naturally high flows are protected, fish migration barrier. The ecological requirements a limit of 10% of the volume of water above base flow for special purpose flows in ACT rivers are not well has been set for abstraction. In the previous guidelines, understood, and no special purpose flows have been flooding flows were termed flushing flows and were identified in these Guidelines. Further ecological defined as the flood events of 1.5 to 2.5 year annual research may lead to a need for special purpose recurrence interval. These were protected by limiting flows for such purposes, for example, as maintaining abstraction in a water management area to 10% of the spawning of native fish species in the Cotter River. volume of flows above the 80th percentile. This threshold was set using the best available scientific advice on the Impoundment drawdown levels for provision of habitat diversity and quality, nutrient and Urban lakes sediment cycling, movement of biota and connectivity Urban lakes are constructed water features, designed to between aquatic and terrestrial habitats. The knowledge protect downstream reaches from the effects of urban gained by research on the effects of flushing flows of runoff. Macrophytes in urban lakes are recognised a range of volumes in the water supply areas indicates as an important ecological asset. Macrophyte stands that the provision of such volumes of water is a low risk are a significant component of aquatic habitat, and approach. their destruction would affect dependent biota and associated ecosystem processes including sedimentation, nutrient cycling and water chemistry.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 23 The water levels in lakes, ponds and reservoirs Temporary requirements influence the survival and recruitment of submerged In any subcatchment, there may be circumstances and emergent macrophytes. If the water level of urban in which it is necessary to reduce the volume of lakes and ponds is lowered too far below spillway level environmental flows for a limited time. The types of for a significant period, macrophyte zonation may be incidents that could trigger the need for reduced flows significantly changed, compromising the ecological could be: values of those waterbodies and their capacity to support other environmental functions. >> oil spill or other contamination within the catchment requiring the cessation of releases; However, waterbodies with a water level regime that fluctuates within a reasonable range at the right >> infrastructure failure, planned maintenance or frequency and seasonality can support a diverse upgrades requiring reduction in flow downstream and resilient macrophyte community with beneficial of a dam; zonation. Stable water levels can result in static and >> landslides affecting water quality; fragile macrophyte communities whilst dramatic >> to meet competing environmental objectives, such water level variations can result in very limited or no as maintaining Cotter Reservoir at a level suitable macrophyte communities. for fish passage by drowning out barriers; or In the 2006 Guidelines a maximum drawdown >> other incidents. limit of 0.20m was set for urban lakes to protect Conversely there may be times when additional macrophytes as an important ecological component environmental flows are identified for ecological of such systems. A drawdown of this extent would purposes. Environmental flow volumes and duration expose approximately 2-3m of the lake shoreline have been determined based on best available science and the macrophytes in this zone, which poses low or expert opinion. However, it is possible that, as risk to existing macrophytes. Recent research and further understanding is gained, a need for a particular investigations into drawdown levels in Canberra’s short-term flow component is identified. Examples of urban ponds indicates that a higher drawdown level increased flows for ecological purposes could include: of up to 0.60m represents a low risk to macrophytes. The 2017 review extended the potential fluctuation of >> additional riffle or pool maintenance flows following water level in urban ponds, lakes and wetlands to 0.60 storm events; m, where this aligns with seasonal variation. • drown out of fish migration barriers to facilitate access to spawning areas; or There is already a significant demand for use of water from urban waterbodies for such purposes >> other ecological requirements. as irrigation of parklands and playing fields, and for Flows required to meet both these sorts of irrigation of golf courses. If ponds are drawn down requirements are termed temporary requirements. excessively and repeatedly, then the macrophytes In order for these flows to be implemented, the may diminish or disappear over time resulting in Environment Protection Authority would need to declining water quality. More flexible drawdown limits be satisfied of the need for the change to flows. than provided by these Guidelines can be applied Temporary requirements are not intended to apply to to abstraction activities if they are accompanied by drought situations, and it is envisaged that changes a specific monitoring and assessment program. In to flows would apply for a limited period until the the absence of monitoring and assessment, having a incident or situation was resolved. precautionary limit of 0.60m on the drawdown level of lakes and ponds is considered to be an effective and Water supply drought flows efficient approach for the protection of urban lakes or ponds. A water supply drought is a concept describing an abnormally dry period resulting in not enough water Thus, these Guidelines allow water level fluctuations of for human needs. Urban communities experience a up to 0.60 m below full supply level while continuing to water supply drought when there is insufficient water protect waterbird breeding habitat during breeding by available in reservoirs to allow normal domestic limiting drawdown to 0.2 m during July to November consumption. Aquatic ecosystems, under natural inclusively. conditions, have adapted resistance and resilience to a full range of climatic conditions, including very dry periods. In regulated systems these dry periods can cause additional stress and it is important to minimise additional stress on these systems during such times.

24 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Temporary requirements In any subcatchment, there may be circumstances in which it is necessary to reduce the volume of environmental flows for a limited time. The types of incidents that could trigger the need for reduced flows could be: >> oil spill or other contamination within the catchment requiring the cessation of releases; >> infrastructure failure, planned maintenance or upgrades requiring reduction in flow downstream of a dam; >> landslides affecting water quality; >> to meet competing environmental objectives, such as maintaining Cotter Reservoir at a level suitable for fish passage by drowning out barriers; or >> other incidents. Conversely there may be times when additional environmental flows are identified for ecological Nevertheless, the Guidelines need to reflect the Water supply drought flows will be applied in two purposes. Environmental flow volumes and duration influence of flow requirements on provision of a stages, reflecting the stages of water restrictions have been determined based on best available science domestic water supply during dry periods, and do placed on domestic water consumption: so through three mechanisms. Firstly the Guidelines or expert opinion. However, it is possible that, as >> Water supply drought flows under stage 1 accommodate seasonal changes in flow by specifying further understanding is gained, a need for a particular restrictions short-term flow component is identified. Examples of different base flows for each month, calculated using >> Water supply drought flows under stage 2 or more increased flows for ecological purposes could include: historical data. This approach recognises that there are seasonal differences in river flow in the ACT; higher severe restrictions >> additional riffle or pool maintenance flows following in winter and spring than in summer. Secondly, during storm events; Water supply drought flows only apply to water supply non-drought periods in water supply catchments, the catchments, and have different requirements for each • drown out of fish migration barriers to facilitate release requirement for base flows is never larger than reach within the catchment. Water supply drought flow access to spawning areas; or the reservoir inflow. guidelines are detailed in Section 5. >> other ecological requirements. Thirdly by recognising that during extended low Flows required to meet both these sorts of flow periods, it may be necessary to reduce the Flow variability requirements are termed temporary requirements. environmental releases in water supply catchments in Variability in flow is an important characteristic of In order for these flows to be implemented, the line with domestic measures to reduce water use, and upland river systems such as the Cotter and upper Environment Protection Authority would need to so ensure the ongoing security of the water supply. Murrumbidgee Rivers. Static or constant flows (such be satisfied of the need for the change to flows. Water supply drought environmental flows will apply as constant low flow) can have a detrimental effect Temporary requirements are not intended to apply to as defined below. on in-stream biota in the Cotter River system (Norris drought situations, and it is envisaged that changes A water supply drought is defined for the purpose and Nichols 2011, White et al. 2012) and likely in other to flows would apply for a limited period until the of these Guidelines as occurring when the water local streams. Varying flows on a daily basis, where the incident or situation was resolved. supply utility initiates temporary water restrictions variability of flows downstream of an impoundment (DI2010-197). The water utility may introduce are based on inflows or flow in an adjacent Water supply drought flows temporary restrictions in response to low reservoir unregulated tributary, is likely to provide the greatest A water supply drought is a concept describing an levels, poor water quality in water supply reservoirs, benefit to the river. abnormally dry period resulting in not enough water adverse climate forecasts or other factors judged The current flow rules implemented for the reaches for human needs. Urban communities experience a to be relevant. This approach recognises that the downstream of Corin and Bendora Dams recognise water supply drought when there is insufficient water water utility may use a range of information to make the need for frequent flushes to reduce periphyton available in reservoirs to allow normal domestic a decision about restrictions. The Environment and sediment accumulation in riffles. They also consumption. Aquatic ecosystems, under natural Protection Authority must be satisfied that the recognise the operational constraints that prevent conditions, have adapted resistance and resilience to restrictions are necessary to ensure water supply daily flow variation and flows were therefore designed a full range of climatic conditions, including very dry security. During a period of a water supply drought, to be variable for most of the month, a flow pulse periods. In regulated systems these dry periods can different environmental flow requirements termed delivered once a month. This flow regime has been cause additional stress and it is important to minimise water supply drought flows, will apply to ensure shown to meet the ecological objectives (the river additional stress on these systems during such times. security of the ACT water supply (see Section 5). The health outcomes desired) and represents a practical implementation of permanent water conservation approach to flow variability in the Cotter River system. measures (DI2010-279) will not be considered to be water restrictions for the purposes of these Guidelines.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 25 4 ECOLOGICAL OBJECTIVES FOR ACT AQUATIC ECOSYSTEMS

26 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 4 ECOLOGICAL OBJECTIVES FOR ACT AQUATIC ECOSYSTEMS

The purpose of environmental flows is to protect river, stream, lake, and aquifer ecosystems. The setting of ecological objectives allows specific ecological values to be targeted by components of the environmental flow regime. In addition, quantified ecological objectives can be used to assess the effectiveness of environmental flows, and the information can be used to develop an adaptive management approach for environmental flows. Ecological values may be affected by factors other than environmental flow objectives for different reaches. The ecological objectives and indicators identified in Table 2 below are based on recommendations of the CRCFE (Ogden et al 2004) and subsequent revision (Dusting et al 2017), and may be refined based on findings from a monitoring and assessment program (Section 6 Monitoring and Assessment). The scientific basis for recommendations are provided as appendices to the Guidelines. A number of ecological objectives do not have prescribed indicators or have estimated indicators. In the majority of cases this is due to one of three circumstances: 1. Environmental flows cannot be actively managed for particular outcomes in the applicable waterbodies; 2. There is limited capacity to manage water levels for ecological outcomes due to priority of water supply; or 3. Baseline survey data does not exist for the objective, hence accurate indicators cannot be developed. Filling these knowledge gaps is a recommended research priority. See Section 6 and Appendix 3.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 27 TABLE 2: ECOLOGICAL OBJECTIVES FOR ACT AQUATIC ECOSYSTEMS 1 Ecosystem Objective Indicator trigger points and reach 2 Water Supply Catchment Ecosystems Reach upstream To maintain healthy aquatic These reaches provide the reference condition for potentially impacted sites of Corin ecosystems Indicators as per Corin Dam to Bendora Reservoir reach, where applicable

Corin Reservoir To maintain healthy aquatic Non-dominance (<20% cover) of filamentous algae. ecosystems

To maintain populations of Annual catch is at least 1 fish per net night Two-spined Blackfish Corin Dam To maintain populations of Young of the year and year 1+ age classes (<120 mm total length) comprise to Bendora Two-spined Blackfish >30% of the monitoring catch; AND total catch +is >2 blackfish for 80% of Reservoir samples (each 30 m section) in each site across 2 sampling years

To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level ecosystems Non-dominance (<20% cover) of filamentous algae in riffles. Temperature, turbidity and DO mimic natural inflows11 Instream macrophyte cover <20%4 Extent and condition of riparian vegetation is maintained or improved5

To prevent degradation of Sediment deposition is limited to <20% of total depth of pools measured at riverine habitat through base flow using techniques as per Ecowise Environmental (2005). Five yearly sediment deposition monitoring and reporting recommended for all sediment monitoring.

Bendora To maintain populations of Minimum 2 post-juvenile Two-spined Blackfish per fyke net night per year. Note: Reservoir Two-Spined Blackfish Drawdown should be carefully managed around mid-November, as Blackfish eggs and larvae are tied to spawning site for about 6 weeks.

To maintain healthy aquatic Non-dominance (<20% cover) of filamentous algae. ecosystems

To maintain populations of Minimum 2 post-juvenile Cod per fyke net night10 Trout Cod Bendora Dam To maintain populations of Young of the year and year 1+ age classes (<120 mm) comprise >30% of the to Cotter Two-Spined Blackfish monitoring catch; AND catch is >2 fish for 80% samples (30 m section) in each Reservoir reach across 2 sampling years

To maintain populations of Recruitment detected at 80% of monitoring sites. Minimum capture of Macquarie Perch 1 Macquarie Perch (< 150 mm) per net night per site. Annual sampling of 12 net nights per site, 5 sites between Bendora Dam and Cotter Reservoir

To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level ecosystems Non-dominance (<20% cover) of filamentous algae in riffles. Temperature, turbidity and DO mimic natural inflows11 Instream macrophyte cover <20%. Extent and condition of riparian vegetation is maintained or improved5

To prevent degradation of Sediment deposition is limited to <20% of total depth of pools measured at riverine habitat through base flow. Five yearly monitoring and reporting recommended for all sediment sediment deposition monitoring.

Cotter To maintain populations Minimum total catch 3 Macquarie Perch per fyke net night, per year, comprised Reservoir of Macquarie Perch and of > 50% individuals <150 mm Murray River Crayfish Murray River Crayfish detected6

To maintain healthy aquatic Non-dominance (<20% cover) of filamentous algae. ecosystems

28 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Ecosystem Objective Indicator trigger points and reach 2

Downstream of To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level ecosystems Non-dominance (<20% cover) of filamentous algae in riffles Temperature, turbidity and DO mimic natural inflows11.

To maintain riparian Extent and condition of riparian vegetation is maintained or improved vegetation values

Googong To maintain healthy aquatic Non-dominance (<20% cover) of filamentous algae. Reservoir ecosystems

Downstream of To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level Googong Dam ecosystems Non-dominance (<20% cover) of filamentous algae in riffles Temperature, turbidity and DO mimic natural inflows11. Extent and condition of riparian vegetation is maintained or improved5

Natural Ecosystems All reaches To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level ecosystems Non-dominance (<20% cover) of filamentous algae in riffles. Temperature, turbidity and DO mimic natural inflows Instream macrophyte cover <20%

Modified Ecosystems Murrum-bidgee To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level River (ACT ecosystems in terms of biota Non-dominance (<20% cover) of filamentous algae in riffles. reaches) To enhance native fish Recruitment of Murray Cod detected at 80% sites in reach across 2 sampling community, including years. Current monitoring techniques unsuitable for use even for detection 6 Murray Cod and Murray River Crayfish3 To prevent degradation of Sediment deposition is limited to <20% of total depth of pools measured at riverine habitat through base flow sediment deposition

To maintain extent of riparian Instream macrophyte cover <20% 5 vegetation

To maintain diversity and Knowledge gaps are currently too broad to devise meaningful indicators increase abundance of waterbirds.

Lake Burley To maintain and improve Presence of emergent macrophytes of sufficient density and diversity to Griffin functional assemblages of perform beneficial WQ processes and provide habitat for desired fauna.4 macrophytes Submerged macrophytes present at density that perform beneficial WQ processes 4

To enhance native fish NCA target (for information only): Presence of Murray Cod and Golden Perch community, including detected at 80% sites during fish surveys Murray Cod and Golden Perch To maintain diversity and NCA target (for information only): Maintain a viable Silver Gull population on abundance of waterbirds Spinnaker Island

Wetlands To maintain and improve Presence of emergent macrophytes of sufficient density and diversity to functional assemblages of perform beneficial WQ processes and provide habitat for desired fauna. 4 macrophytes Submerged macrophytes present at density that perform beneficial WQ processes 4

To maintain healthy aquatic Knowledge gaps are currently too broad to devise meaningful indicators 7 ecosystems in terms of biota

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 29 Ecosystem Objective Indicator trigger points and reach 2

Other Modified To maintain healthy aquatic Macroinvertebrate assemblages are maintained at AUSRIVAS band A level Reaches ecosystems in terms of biota Non-dominance (<20% cover) of filamentous algae in riffles.

Enhance native fish Upstream of LBG: Murray Cod present and detected at 80% of sites across 2 community in Molonglo R. years Upstream and Downstream Downstream of LBG: None identified of LBG

To prevent degradation of Sediment deposition is limited to <20% of total depth of pools. riverine habitat through Median suspended solids load from rural catchments less than 5,000kg/km2/yr. sediment deposition

To maintain and improve Presence of emergent macrophytes of sufficient density and diversity to functional assemblages of perform beneficial WQ processes and provide habitat for desired fauna. macrophytes in modified Submerged macrophytes present at density that perform beneficial WQ lakes, ponds and wetlands processes

To maintain and improve Knowledge gaps are currently too broad to devise meaningful indicators5 riparian vegetation in Molonglo R. Downstream of LBG

To maintain and improve Knowledge gaps are currently too broad to devise meaningful indicators populations of platypus and other vertebrate fauna in Molonglo R. Downstream of LBG

Urban Ecosystems Urban streams To prevent degradation Turbidity does not exceed guidelines for freshwater ecosystems 80% of the of downstream aquatic time9 ecosystems through sediment Median suspended solids load from urban catchments less than 10,000 kg/ deposition and high flow km2/yr. rates Peak flows not greater than natural flows for large peak flows.

To maintain healthy aquatic For unlined streams only: ecosystems in terms of biota Macroinvertebrate assemblage long-term improvement as measured by AUSRIVAS Non-dominance (<20% cover) of in-stream macrophytes

Urban lakes, To maintain functional Presence of emergent macrophytes of sufficient density and diversity to ponds and assemblages of macrophytes perform beneficial WQ processes and provide habitat for desired fauna (to be wetlands in urban lakes and ponds determined but for wetlands is expected to be >20%). Submerged macrophytes present at density that perform beneficial WQ processes (to be determined)

To maintain healthy aquatic Knowledge gaps are currently too broad to devise meaningful indicators ecosystems in terms of biota

To maintain populations Fish kills of key species do not occur except for when being undertaken as of native fish in urban managed biocontrol for pest fish species eg redfin and European carp. Noting impoundments where fish kills should not, but may occur, during water body drawdown/refill. stocking occurs

To protect waterbird breeding Knowledge gaps are currently too broad to devise meaningful indicators habitat from drawdown during breeding season

30 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Ecosystem Objective Indicator trigger points and reach 2 The rationale for most of the changes to the above table since the 2013 Guidelines are outlined in Appendix 3. Locations of downstream of dam monitoring sites needs to be approved by the EPA. The BWS (Table 8) recommends ACT reaches of the Murrumbidgee River as candidate sites for the establishment of additional populations of Silver Perch. Silver Perch are functionally extinct within the ACT and the only way to establish additional populations in the ACT is to undertake a stocking program. This is outside the scope of the EFG. For macrophyte coverage, baseline data needs to be collected before this Indicator is implemented. 5. Riparian vegetation method and baseline data needs to be collected before this Indicator is implemented. Rapid Appraisal of Riparian Condition (RARC, Jansen et al, 2005) or other method to be developed which is better suited to the ACT’s upland zones. 6. Current monitoring techniques for Murray River Crayfish are considered unsuitable to provide a reliable method for detection, 7. Information has been collected by Waterwatch volunteers on frogs, birds and macroinvertebrates, and some signal based scoring. Investigations into linkages with water levels/flows needs to be undertaken to confirm the value of these attributes as indicators. There is also currently work to identify AUSRIVAS style assessments for wetlands so that macroinvertebrate data can be useful. 8. Data analysis indicates that annual sampling for Blackfish and Macquarie Perch is much better than biannual sampling, for reducing the risks of unnecessary management eg false negative results. 9. Turbidity downstream of lakes, ponds and wetlands should be the measuring point because the function of these systems is to trap sediment at the water body point. 10. Trout Cod were stocked in Bendora reservoir in the 1980s, hence the indicator is a trigger to identify recruitment issues with the current population. 11. Where possible, within the operational constraint of supplying the best water for treatment and distribution, the water utility will endeavour to release water downstream of the water supply dams that is similar or better than the temperature, turbidity and DO of the water entering the reservoir.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 31 5 ENVIRONMENTAL FLOWS FOR PARTICULAR ECOSYSTEMS

32 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 5 ENVIRONMENTAL FLOWS FOR PARTICULAR ECOSYSTEMS

Environmental flows have been established for each of the ecosystem types, and for specific reaches within the water supply catchments. The environmental flows are designed to maintain the ecological objectives determined in Section 4. Environmental flows for each ecosystem category and specific reaches within are summarised in Table 3 and discussed in detail in this Section.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 33 TABLE 3A: SUMMARY OF ENVIRONMENTAL FLOW REQUIREMENTS FOR THE ACT Ecosystem Reach Flow Requirement Category

Base Flows Water Supply Upstream of Corin Reservoir Maintain all natural flows Ecosystems Upstream of Googong Reservoir Maintain all natural flows except those needed for stock and domestic purposes, and that already provided for at the time these guidelines are listed (NSW responsibility).

Corin Dam to Bendora Reservoir Maintain 75% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less.1

Bendora Dam to Cotter Reservoir Maintain 75% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less.

Weekly variation in flows reduced from 50% to 25% during Macquarie Perch breeding season (October – December inclusive).

Downstream Cotter Dam Maintain 15% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less.3

Downstream Googong Dam Maintain 50% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less.4

Natural All reaches in natural ecosystems Maintain 80th percentile monthly flow in all months. Abstractions may not Ecosystems exceed 10% of flow above these flow rates.

Modified Murrumbidgee River Maintain 80th percentile monthly flow November – May, and 90th percentile Ecosystems monthly flow June –October inclusive. With a minimum flow of 50ML/d protected in January to March. Tantangara Dam environmental flow releases may not be abstracted within the ACT.

Other reaches in the ACT in Maintain 80th percentile monthly flow in all months. Abstractions may not modified ecosystems exceed 10% of flow above these flow rate.

Wetlands Maintain 80th percentile monthly flow in all months. Abstractions may not exceed 10% of flow above these flow rate.

Urban Urban streams Maintain 80th percentile monthly flow in all months. Abstractions may not Ecosystems exceed 10% of flow above these flow rate.

Manage flows to reduce runoff volumes, velocities and pollution transport to downstream ecosystems.

Riffle Maintenance Flows Water Supply Corin Dam to Bendora Reservoir Maintain a flow of 150 ML/Day for 3 consecutive days every 2 months Ecosystems Bendora Dam to Cotter Reservoir Maintain a flow of 150 ML/Day for 3 consecutive days every 2 months

Below Cotter Dam Maintain a flow of 100 ML/Day for 1 day every 2 months

Below Googong Dam Maintain a flow of 100 ML/Day for 1 day every 2 months

Natural All reaches in Natural Ecosystems Riffle maintenance flows are not required Ecosystems

Modified Murrumbidgee River Protect a minimum of 195 ML/d natural flow for a period of 1 day, once every Ecosystems 30 days.6

All other reaches in Modified Riffle maintenance flows are not required Ecosystems

Urban All reaches in Urban Ecosystems Riffle maintenance flows are not required Ecosystems

34 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Ecosystem Reach Flow Requirement Category

Pool Maintenance Flows Water Supply Corin Dam to Bendora Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and Ecosystems mid- October

Bendora Dam to Cotter Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October2

Below Cotter Dam Not required

Below Googong Dam Not required

Channel Maintenance Flows Natural All reaches in Natural Ecosystems Protect 90% of the volume in events above the 80th percentile from abstraction Ecosystems

Modified All reaches in the ACT including Protect 90% of the volume in events above the 80th percentile from abstraction Ecosystems the Murrumbidgee5

Urban All reaches in urban ecosystems Protect 90% of the volume in events above the 80th percentile from abstraction Ecosystems

Groundwater Abstraction Limits Water Supply All Reaches Groundwater abstraction is limited to 10% of the long term recharge Ecosystems

Natural All reaches in natural ecosystems Groundwater abstraction is limited to 10% of the long term recharge Ecosystems

Modified All reaches in the ACT including Groundwater abstraction is limited to 10% of the long term recharge Ecosystems the Murrumbidgee

Urban All reaches Groundwater abstraction is limited to 10% of the long term recharge Ecosystems

Impoundment Drawdown Levels Water Supply Cotter Reservoir An adaptive management program will be used to guide drawdown to protect Ecosystems Macquarie Perch

Natural All natural lakes or ponds No abstraction is permitted from natural lakes or ponds Ecosystems All other impoundments Drawdown is limited to 0.20m below the spillway1&2

Modified All impoundments Drawdown is limited to 0.20m below the spillway1&2 Ecosystems Jerrabomberra Wetlands Allow periodic drawdown (through drought or LBG changes)

Lake Burley Griffin Allow water level fluctuations of up to 0.6 m below full supply level. Limit drawdown to 0.2 m July-November (to protect waterbird breeding)

Wetlands Protect natural flow and water level regime

Urban All impoundments Allow water level fluctuations of up to 0.6 m below full supply level, where Ecosystems possible

Limit drawdown to 0.2 m July-November (to protect waterbird breeding) 1 To incorporate flow variability and seasonal patterns: Base flows: 75% of the 80th percentile (calculated monthly) or inflows whichever is less Riffle maintenance flows made up of 25% of the 80th percentile (calculated monthly) delivered over 2-3 days every month. 2. Flow requirements downstream of dams can be met by releases and/or spillway flows. The target needs to be met as far as reasonably practicable. For Bendora, with limited release capacity, coordination with downstream tributary flows can also be used. 3. The flow requirement for downstream of Cotter Dam is equivalent to the previous requirement of 15ML/d but modified to provide variability and seasonality of flows. Note that this is still exceeded by the Commonwealth requirement of an average flow of 34ML/d. 4. The flow requirement for downstream of Googong Dam is equivalent to the previous requirement of 10ML/d but modified to provide variability and seasonality of flows. See also section 5.1.3. 5. For the Murrumbidgee River channel maintenance flows, see section 5.3.1. 6. As described in Icon Water (2015) M2G streamflow and water quality management plan.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 35 TABLE 3B: SUMMARY OF ENVIRONMENTAL FLOW REQUIREMENTS FOR THE ACT TABLE 3C: SUMMARY OF ENVIRONMENTAL FLOW REQUIREMENTS FOR THE ACT Drought Flows for Water Supply Ecosystems: Stage 1 restrictions Drought Flows for Water Supply Ecosystems: Stage 2 restrictions or above Reach Flow Requirement Reach Flow Requirement

Base Flows Base Flows Upstream of Corin Reservoir Maintain all natural flows Upstream of Corin Reservoir Maintenance of all natural flows

Upstream of Googong Dam Maintain all natural flows except those needed for stock and domestic purposes, and that Upstream of Googong Dam and Maintenance of all natural flows except those needed for stock and domestic purposes, and already provided for at the time these guidelines are listed (NSW responsibility). any impoundment on the Naas / that already provided for at the time these guidelines are listed (NSW responsibility). Gudgenby Rivers Corin Dam to Bendora Reservoir Maintain a flow of 40 ML/day or 75% of the 80th percentile of the monthly natural inflow, or natural inflow whichever is lesser volume Corin Dam to Bendora Reservoir Maintain an average flow of 20 ML /day or inflow, whichever is lower.

Bendora Dam to Cotter Reservoir Maintain a flow of 40 ML/day or 75% of the 80th percentile of the monthly natural inflow, or Bendora Dam to Cotter Reservoir Maintain an average flow of 20 ML /day or inflow, whichever is lower. natural inflow whichever is lesser volume Downstream of Cotter Dam Maintain 15% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less1 Downstream of Cotter Dam Maintain 15% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less1 Downstream of Googong Dam Maintain 50% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less2 Downstream of Googong Dam Maintain 50% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less1 Riffle Maintenance Flows Murrumbidgee River Protect natural flows shown in Icon Water (2015) under drought conditions 6 Tantangara Dam Corin Dam to Bendora Reservoir Maintain a flow of 150 ML/day for 3consecutive days every 2 months environmental flow releases may not be abstracted within the ACT. Bendora Dam to Cotter Reservoir Maintain a flow of 150 ML/day for 3 consecutive days every 2 months Riffle Maintenance Flows Downstream of Cotter Dam Not required Corin Dam to Bendora Reservoir Maintain a flow of 150 ML/day for 3 consecutive days every 2 months Downstream of Googong Dam Not required Bendora Dam to Cotter Reservoir Maintain a flow of 150 ML/day for 3 consecutive days every 2 months

Downstream of Cotter Dam Not required Pool Maintenance Flows Corin Dam to Bendora Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October Downstream of Googong Dam Not required Bendora Dam to Cotter Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October Pool Maintenance Flows Downstream of Cotter Dam Not required Corin Dam to Bendora Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October Downstream of Googong Dam Not required Bendora Dam to Cotter Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October 1. The flow requirement for downstream of Cotter Dam is equivalent to the previous requirement of 15ML/d but modified to provide variability and Downstream of Cotter Dam Not required seasonality of flows. Note that this is still exceeded by the Commonwealth requirement of an average flow of 34ML/d. 2. The flow requirement for downstream of Googong Dam is equivalent to the previous requirement of 10ML/d but modified to provide variability Downstream of Googong Dam Not required and seasonality of flows. See also section 5.1.3. 1. The flow requirement for downstream of Cotter Dam is equivalent to the previous requirement of 15ML/d but modified to provide variability and seasonality of flows. Note that this is still exceeded by the Commonwealth requirement of an average flow of 34ML/d. 2. The flow requirement for downstream of Googong Dam is equivalent to the previous requirement of 10ML/d but modified to provide variability and seasonality of flows. See also section 5.1.3.

36 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES TABLE 3C: SUMMARY OF ENVIRONMENTAL FLOW REQUIREMENTS FOR THE ACT Drought Flows for Water Supply Ecosystems: Stage 2 restrictions or above Reach Flow Requirement

Base Flows Upstream of Corin Reservoir Maintenance of all natural flows

Upstream of Googong Dam and Maintenance of all natural flows except those needed for stock and domestic purposes, and any impoundment on the Naas / that already provided for at the time these guidelines are listed (NSW responsibility). Gudgenby Rivers

Corin Dam to Bendora Reservoir Maintain an average flow of 20 ML /day or inflow, whichever is lower.

Bendora Dam to Cotter Reservoir Maintain an average flow of 20 ML /day or inflow, whichever is lower.

Downstream of Cotter Dam Maintain 15% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less1

Downstream of Googong Dam Maintain 50% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less2

Riffle Maintenance Flows Corin Dam to Bendora Reservoir Maintain a flow of 150 ML/day for 3consecutive days every 2 months

Bendora Dam to Cotter Reservoir Maintain a flow of 150 ML/day for 3 consecutive days every 2 months

Downstream of Cotter Dam Not required

Downstream of Googong Dam Not required

Pool Maintenance Flows Corin Dam to Bendora Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October

Bendora Dam to Cotter Reservoir Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid- October

Downstream of Cotter Dam Not required

Downstream of Googong Dam Not required 1. The flow requirement for downstream of Cotter Dam is equivalent to the previous requirement of 15ML/d but modified to provide variability and seasonality of flows. Note that this is still exceeded by the Commonwealth requirement of an average flow of 34ML/d. 2. The flow requirement for downstream of Googong Dam is equivalent to the previous requirement of 10ML/d but modified to provide variability and seasonality of flows. See also section 5.1.3.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 37 5.1 WATER SUPPLY ECOSYSTEMS Reaches upstream of all impoundments The primary use of waterbodies in water supply Ecological objectives catchments is provision of a potable water supply. >> To maintain healthy aquatic ecosystems in all Although protection of aquatic ecosystems is a natural ecosystems. designated secondary goal in these areas, the primary The reach upstream of Corin reservoir is unregulated function may require substantial drawdown of reservoirs and has a natural flow regime and high conservation and abstraction from streams. Nevertheless, as a value. Within this region there is to be no interruption consequence of the protected nature of the Cotter to natural flows to achieve both conservation and catchment, this system contains valuable aquatic water supply objectives. ecosystems. For example, apart from the Murrumbidgee River, the Cotter River, along with the Goodradigbee For the Googong, Tinderry and Burra subcatchments River, has the highest number of threatened fish species there should be no abstraction of inflows except that of any river in the ACT or surrounding region. Reservoirs necessary for stock and domestic purposes and that should be managed primarily for water supply, but are already provided for at the time these guidelines complementary ecological benefits should be sought are listed. While the ACT has no statutory responsibility within the bounds of operational restrictions for management of the Googong Reservoir catchment to ensure compliance with the Seat of Government At present the Cotter River catchment from the Acceptance Act 1909, the ACT considers that any boundaries of the headwaters to the Cotter Dam is the abstraction of natural flows should not be greater than only catchment in this category in the ACT. While the that necessary to support best practice traditional Queanbeyan River is a water supply river for the ACT, grazing enterprises. regulation of its catchment area that is outside of the Googong Foreshore Area is under the control of NSW. Reaches between impoundments used as However, the ACT expects the NSW management of a conduit for water supply between Corin the catchment to be consistent with its water supply and Bendora Dams and between Bendora function as provided for by the Seat of Government and Cotter Dams Acceptance Act 1909. For the Googong Foreshore Area, Ecological objectives and for releases from Googong Dam, environmental flow requirements for water supply ecosystems will apply. The ecological objectives for the reaches between Corin Dam and Bendora Reservoir and between In water supply catchments, environmental flows are Bendora Dam and Cotter Reservoir are: not expected to mimic natural conditions; if this were >> To maintain populations of Two-spined Blackfish the case, there would be a significant reduction in (both reaches); ; the available volume of potable water supply, which would pose a risk to the security of the domestic water >> To maintain riparian vegetation values supply. An alternative approach has been adopted; >> To maintain healthy aquatic ecosystems (both reaches) identifying ecological values that are expected to >> To prevent degradation of riverine habitat through be maintained by environmental flows, and the sediment deposition (both reaches) associated flows required to achieve the ecological outcomes. Different types of reaches in water >> To maintain populations of Macquarie Perch supply ecosystems are identified in order to specify (Bendora Dam to Cotter Reservoir). appropriate flows. These reaches are listed in Table The approach taken has been to base guidelines on 4. Environmental flow requirements for these types the flow requirements that maintain these ecological of reaches are summarised in Table 3, and are also objectives with a minimum safety standard. described below in Table 4.

TABLE 4: WATER SUPPLY REACHES Reach Type River Reach

Reaches upstream of all impoundments Cotter River Upstream of Corin Reservoir

Queanbeyan River Upstream of Googong Reservoir

Reaches between impoundments used as a conduit for Cotter River Between Corin Dam and Bendora Reservoir water supply Cotter River Between Bendora Dam and Cotter Reservoir

Reaches downstream of impoundments not used as a Cotter River Downstream of Cotter Dam conduit for water supply Queanbeyan River Downstream of Googong Dam

38 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Base flows It is recognised that on occasions there may be In all months in all years the defined base flow is to significant volumes of water flowing over the dam be protected. The base flow is defined as 75% of the spillway. If such a flow occurs of a volume and duration 80th percentile of water flowing into the reservoir or equal to the required riffle maintenance flow, it will the natural inflow, whichever is less. That is, flows be considered to be a riffle maintenance flow and the entering the reservoir, up to and including 75% of the next riffle maintenance flow will not be required for 80th percentile are to be released. This flow rate does two months +/- 1 week. not easily translate to a fixed percentile; depending on Downstream of both Bendora and Corin Dams, the reach and the month this equates to a flow rate the riffle maintenance flow is to be measured at between the 85th and 90th percentile. the gauging station downstream of the dam wall. The base flow volume required was determined from If additional gauging stations are installed in the experience with environmental releases in the Cotter reaches downstream of either dam, or additional River. Where baseflow is released from a dam with information provided, the point at which the riffle outlet controls the baseflow should not be held at maintenance flow is measured may be changed if it a constant discharge for the month. Research and can be demonstrated that any changes still ensure assessment of various baseflow volumes and release that the riffle maintenance function of the flows is regimes in the Cotter River indicate that varying being achieved. the discharge over a two week period can mitigate some of the effects caused by low constant flows, by Pool maintenance flow assisting fish migration and connectivity. In effect once A pool maintenance flow of >550 ML/day for two the monthly volume has been determined, greater consecutive days is to be provided between mid ecological benefits can be obtained with fortnightly July and mid October. Three sources of water may variations in the rate of release of that monthly volume comprise a pool maintenance flow; tributary inflows, even though the total monthly volume remains the water flowing over the dam spillway or releases from same. the dam. Weekly variation in flows should be reduced (from It is recognised that there may not be the 50% to 25%) during Macquarie Perch breeding season infrastructure capacity to safely release the full pool (October – December inclusive, Bendora Dam to maintenance flow and that the flow may need to be Cotter Reservoir). Reduction in the variation during implemented by making a dam release in conjunction this period is aimed at reducing the likelihood of with a tributary inflows or dam overtopping. egg stranding or egg displacement and assisting fish If the pool maintenance flow is met solely by tributary migration past low flow barriers. inflows, then this flow will not be considered a riffle maintenance flow as experience has shown that Riffle maintenance flow during the falling leg of an event of this size, significant In the water supply catchments, riffle maintenance sediment can be deposited in riffle areas. flows are not designed to mimic the pattern of natural flows; they are specified to achieve ecological If the pool maintenance flow has been augmented by outcomes. As such, regular riffle maintenance flows water flowing over the dam spillway or releases from are designed to flush sediment from riffles to achieve the dam, then this flow will also be considered to be a the outcome normally provided by the irregular riffle maintenance flow. flushing flows that would occur naturally. A riffle maintenance flow of 150 ML/Day for three consecutive Downstream of Bendora Dam, the pool maintenance days is to occur every two months. Riffle maintenance flow is to be measured at Vanities Crossing gauging flows can be met by a sufficient volume of water station, and downstream of Corin dam, the flow is to flowing over the dam spillway, a release through the be measured at the gauging station downstream of the dam valves or a combination of these sources. Each dam wall. If additional gauging stations are installed time a riffle maintenance flow occurs, either by spill in the reaches downstream of either dam, the point at or by release, the next flush is required within the next which the pool maintenance flow is measured may be two months +/- 1 week. changed if it can be demonstrated that any changes still ensure that the pool maintenance function of the The riffle maintenance flow has been determined flows is being achieved. from the monitoring of riffle condition in the Cotter River before and after a series of experimental riffle maintenance flows. The effect of the riffle maintenance flows on the identified ecological objectives and indicators will continue to be monitored and assessed.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 39 Drought flows - stage 1 restrictions Base flows During a defined water supply drought the following Downstream of Cotter Dam 15% of the 80th percentile flow requirements apply for the reaches between or inflows whichever is less Corin Dam and Bendora Reservoir, and between Downstream of Googong Dam 50% of the 80th Bendora Dam and Cotter Reservoir. percentile or inflows whichever is less Under stage 1 restrictions the domestic water supply Incorporate flow variability and seasonal patterns into is under threat and a reduction in environmental flow base flow requirements is appropriate to protect supply security while still protecting ecosystem values. The base flows downstream of the most downstream impoundments in the water supply catchments are The base flow requirement is an average of 40 ML/day, or specified as minimum channel wetting volumes in 75% of the 80th percentile, or natural inflow, whichever recognition that these reservoirs are the final capture is the lesser volume. It is anticipated that licensing point for domestic supply. A channel wetting volume requirements will ensure a scheme of variable low flow is the flow that covers a reasonable proportion releases around the average of the daily base flow. of a specified riffle, allowing adequate habitat for Riffle maintenance and pool maintenance flows periphyton, macroinvertebrates, and fish to be wetted remain the same as for non-drought periods. at all times. Channel wetting flows were established by an ‘expert panel’ approach and have been validated Drought flows - stage 2 or more severe restrictions by specific research and monitoring on base flow Under stage 2 or more severe restrictions the volumes in each reach. Note that under particular flow domestic water supply is under significant threat conditions, Icon Water’s Licence to Take Water (WU67) and a significant reduction in environmental flow stipulates alternative flow requirements to be enacted. requirements is appropriate to protect supply security. This reduced flow regime poses an increased risk of Compliance is also required by Icon Water for degradation to the aquatic ecosystem; the river would the Enlarged Cotter Dam (ECD) environmental be expected to recover from a short-term reduction requirements as specified in the conditions of the in flow of this magnitude, but a long term reduction Public Environment Report from the Commonwealth would result in degradation. Government and the Development Application from the ACT Government, following the ECD Environmental The base flow requirement is an average 20 ML/day. Impact Assessment process. 34ML/day environmental The licensing requirements will ensure a scheme of flow (12 month rolling average) is the Commonwealth variable low flow releases around the average of the requirement. As identified by EFTAG, flow variability daily base flow. and seasonal patterns need to be provided by Icon Riffle maintenance and pool maintenance flows Water in the base flows. remain the same as for non-drought periods. Fulton et al (2010) showed instream and riparian vegetation was important for crayfish in the lower Reaches downstream of impoundments Cotter.

Downstream of Cotter Dam As there are works to improve the riparian condition Downstream of Googong Dam of the downstream of Googong reach and to minimise landuse impacts in the catchment, there is considered Ecological objectives a significant opportunity for improvement by The ecological objectives for the reaches downstream investigating increases in environmental flows in this of impoundments are: reach, to try to improve the river health. To this end >> To maintain riparian vegetation values downstream Appendix 3 recommends increasing environmental of Cotter Dam releases up to 75% of the 80th percentile flow, plus riffle maintenance flows to 25% of the 80th percentile >> to maintain healthy aquatic ecosystems flow. These flows should be trialled over the next 5 downstream of Cotter Dam; years. This would increase environmental flows from >> to maintain healthy aquatic ecosystems Googong Dam by about 4GL per annum. downstream of Googong Dam; Riffle maintenance flow In the water supply catchments riffle maintenance flows are not designed to mimic natural flows, rather they are managed for specific ecological outcomes. As such, regular riffle maintenance flows are required instead of irregular flows as would occur naturally.

40 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES A riffle maintenance flow of 100 ML/day for one Water quality day is to occur every two months. Each time a riffle Reservoir releases to meet environmental flow maintenance flow occurs either by spill, or by release, requirements should be of a water quality similar to the next flush must occur two months +/- 1 week after that of natural inflows as far as possible. Of particular the last riffle maintenance flow. concern are water temperature and dissolved oxygen. Water from the lower layers of deep, stratified Pool maintenance flow reservoirs can have a much lower temperature and No pool maintenance flows are specified for reaches oxygen content than surface waters. If this bottom downstream of final impoundments. If further water is released to meet environmental flow monitoring and assessment determine the need for requirements, water quality may compromise the pool maintenance flows, they can be provided as a value of the release for the maintenance of aquatic temporary requirement. ecosystems. For example most native fish species use both water temperature and flow as cues for Drought flows – all levels of restriction reproduction, and a cold-water release may severely During a defined drought the following flow disrupt spawning migrations and reproductive activity. requirements apply downstream of Cotter Dam and Googong Dam, for all levels of water restrictions. The Another issue that has arisen is the release of turbid base flow downstream of Cotter Dam will be15 ML/day. water from ACT reservoirs. Normally reservoirs act to The base flow downstream of Googong will be 10 ML/ trap sediment and releases have lower sediment levels day or natural inflow whichever is less. than inflows. In some situations a layer of highly turbid water has persisted in ACT reservoirs with the potential Riffle or pool maintenance flows for these reaches to compromise the quality of the entire reservoir when are not required during drought. If further monitoring bottom waters mixed with surface layers during winter. and assessment determine the need for riffle or It may be desirable from a water supply perspective pool maintenance flows, they can be provided as a to release this turbid water. Such releases need to be temporary requirement. managed to protect downstream ecological values. Water with high turbidity can reduce the abundance Requirements applying to all water supply and diversity of macroinvertebrates. To minimise ecosystems the potential impact of turbid releases, clean water Impoundment drawdown levels releases may be required before and after a turbid Guidelines have been established to control the release to protect aquatic ecosystems downstream. drawdown of the Cotter Reservoir to protect habitat Water quality issues can also arise when flows remain for Macquarie Perch. Between the late 1960s and at a steady low volume. For example, constant low 2004 the Cotter Reservoir was not an active part of flows cause periphyton to accumulate in thick layers, the ACT water supply, and so drawdown was not an trapping sediment and organic matter that can issue. The only successfully breeding ACT population degrade water quality by lowering dissolved oxygen of the endangered Macquarie Perch lives principally levels and changing pH levels (Stevenson 1996). To in the Cotter Reservoir and the Cotter River upstream minimise this effect base flow releases should be of the reservoir. The Cotter Reservoir population was varied by as much as 50% around the recommended reliant on the emergent macrophytes and boulder volume, noting the restrictions on this around the piles around the margins of the reservoir as its main Macquarie Perch breeding season. shelter habitat. The construction of the enlarged Cotter Dam changed the nature and extent of potential Implementation of environmental flows habitat for the Macquarie Perch and large amounts of Environmental flows downstream of impoundments artificial habitat were placed in the new reservoir to are implemented through a combination of releases accommodate this change. The Reservoir is operated and water flowing over the dam spillway. In the case in such a manner that fish habitat is available and of pool maintenance flows, these are supplemented connectivity with the Cotter River is provided during by tributary inflows. Water released to achieve fish spawning periods. Drawdown limits are not set environmental flow requirements should be at a for other water supply reservoirs, though drawdown temperature approximating as closely as possible may impact on the breeding of threatened fish in these that of inflow water. If inflow water temperature reservoirs. is unknown, it should be assumed to be the same as surface water in the reservoir. Where the flow requirement is based on a flow percentile, percentiles should be calculated on a monthly basis but the volume so determined should be released in a manner to include short-term variability.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 41 5.2 NATURAL ECOSYSTEMS Flooding flows 5.3 MODIFIED ECOSYSTEMS Flooding flows, particularly channel maintenance Waterbodies in the natural ecosystem category include flows, are to be protected by restricting abstraction Rivers, lakes and streams in the modified ecosystem those within Namadgi National Park excepting the in water management areas to 10% of the flow above category include those waterbodies outside Namadgi Cotter River Catchment, and those within Tidbinbilla the 80th percentile. The discharge most critical at National Park, Tidbinbilla Nature Reserve and Nature Reserve. These are ecosystems that have determining the width, depth and meander frequency the Canberra urban area. Lake Burley Griffin and persisted in a relatively natural state from a period prior of channels is the 1.5 to 2.5 year annual recurrence the Molonglo River are also considered modified to European settlement. The primary management interval flood event. ecosystems. These ecosystems have been modified by goal for these ecosystems is the conservation of their catchment activities including landscape change, and natural state, and these ecosystems are secondarily Specific conditions that can be placed on licenced modifications to the natural flow regime. managed for recreation and other purposes. abstracters in relation to infrastructure limitations will also ensure that flooding flows of this magnitude are In modified ecosystems, the Guidelines seek to Ecological objective protected. maintain modified ecosystems in as natural a state >> To maintain healthy aquatic ecosystems in all as possible through management of flows and natural ecosystems. Impoundment drawdown levels abstraction. To achieve these management goals four No abstraction is permitted from natural lakes and ponds. groups of modified ecosystems have been identified: >> To prevent degradation of riverine habitat through sediment deposit Implementation >> Murrumbidgee River; >> To maintain high biodiversity values Environmental flows are to be maintained through >> Lake Burley Griffin restrictions on abstractions as detailed above. >> To maintain riparian zone and in-stream macrophytes >> other ACT reaches including the Molonglo, Paddys, Naas and Gudgenby downstream of Namadgi Water quality Base flows National Park (unless designated as water supply Water quality issues can arise when flows remain In all months in all years the base flow is to be catchments under the Territory Plan); and protected. The base flow is defined as the 80th at a steady low volume. For example, constant low >> reaches in NSW over which the Commonwealth has percentile of flows. In addition, abstractions of surface flows cause periphyton to accumulate in thick layers, paramount rights to the water other than those in water may never exceed 10% of the flow rate above trapping sediment and organic matter that can the Queanbeyan River catchment; the base flow. Abstraction of groundwater is limited to degrade water quality by lowering dissolved oxygen 10% of the recharge rate to protect base flow. levels and changing pH levels (Stevenson 1996). To minimise this impact, abstractions should allow Ecological objective natural flow variability to be maintained. >> To maintain healthy aquatic ecosystems.

42 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 5.3 MODIFIED ECOSYSTEMS Murrumbidgee River environmental flows The NSW water sharing plan for the unregulated Rivers, lakes and streams in the modified ecosystem Murrumbidgee (NOW, 2012), specifies the current category include those waterbodies outside Namadgi environmental flow rules implemented in the NSW National Park, Tidbinbilla Nature Reserve and section of the Murrumbidgee upstream of the ACT. the Canberra urban area. Lake Burley Griffin and In addition, some environmental releases are made the Molonglo River are also considered modified from Tantangara Dam as required by the Snowy ecosystems. These ecosystems have been modified by Hydro Licence, which are in accord with the Snowy catchment activities including landscape change, and Water Inquiry Outcomes Implementation Deed modifications to the natural flow regime. 2002. Environmental flow releases from Tantangara In modified ecosystems, the Guidelines seek to Dam may not be extracted through the ACT. This is maintain modified ecosystems in as natural a state a requirement under the Basin Plan to protect from as possible through management of flows and take, Held Environmental Water (HEW) and Planned abstraction. To achieve these management goals four Environmental Water (PEW).The ACT ensures that groups of modified ecosystems have been identified: environmental flow requirements in the rivers for >> Murrumbidgee River; which it has responsibility are met by flows under the control of the ACT. In consequence, environmental >> Lake Burley Griffin flows from NSW upstream, including releases from >> other ACT reaches including the Molonglo, Paddys, Tantangara Dam, pass through the ACT unaffected by Naas and Gudgenby downstream of Namadgi activity in the ACT as they are effectively protected National Park (unless designated as water supply from extraction through the ACT by existing catchments under the Territory Plan); and environmental flow requirements and limits on take. >> reaches in NSW over which the Commonwealth has paramount rights to the water other than those in the Queanbeyan River catchment;

Ecological objective >> To maintain healthy aquatic ecosystems.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 43 Ecological objective Dyer et al (2014) showed that the combination of low >> To maintain healthy aquatic ecosystems in terms of flow and high temperatures may result in adverse water biota quality conditions for fish in refuge pools and that small >> To prevent degradation of riverine habitat through freshes can provide short term improvements in water sediment deposition quality. During January to March, when flows are at or below the protected flows for more than 2 weeks, pool >> To maintain extent of water dependent riparian and water quality should be monitored to inform adaptive in-channel native vegetation flow management. Further monitoring and research is >> To enhance native fish community, including needed to confirm the benefit of protecting base flows Murray Cod and Murray River Crayfish up to 50ML/d during those months. >> To maintain diversity and increase abundance of Flooding flows waterbirds. Flooding flows, particularly channel maintenance Base flows flows, are to be protected by restricting abstraction In all months in all years the base flow is to be in water management areas to 10% of the flow protected. The base flow is defined as the 80th volume above the 80th percentile. The discharge percentile of stream flow in the months November to most critical at determining the width, depth and May inclusive, and the 90th percentile of stream flow meander frequency of channels is the 1.5 to 2.5 year in the months June to October inclusive. In addition, annual recurrence interval flood event. A restriction based on the precautionary principle, base flows of up of abstraction to flows below that threshold or to 50ML/d are to be protected from abstraction during a restriction on the rate of abstraction that can January to March. See Dyer et al (2014) below. occur during those events, will ensure that channel maintenance flows occur at appropriate frequencies. These flows also ensure the Murrumbidgee to Googong (M2G) environmental requirements are Specific conditions can be placed on licenced abstracters met as specified in the conditions of the Public in relation to infrastructure limitations to ensure that Environment Report from the Commonwealth flooding flows of this magnitude are protected. Government and the Development Application from the ACT Government, following the M2G Other reaches in the ACT Environmental Impact Assessment process. The Icon This group includes the Naas and Gudgenby Rivers Water Stream flow and water quality management downstream of Namadgi National Park, and the plan, outlines how the Commonwealth and ACT Molonglo River conditions are met. The 2015 plan identifies base flow protection rules under drought conditions, as well Ecological Objective as riffle maintenance flow rules, which are over and >> To maintain healthy aquatic ecosystems in terms of above the ACT environmental flow guideline rules biota in Table 3 and this chapter. These rules should be >> To prevent degradation of riverine habitat through considered for inclusion in future environmental flow sediment deposition guidelines and any additional monitoring and research undertaken if needed. >> To maintain and improve functional assemblages of macrophytes in modified lakes, ponds and wetlands Abstraction of groundwater is also limited to 10% of the recharge rate to protect base flow. >> To maintain and improve riparian vegetation in Molonglo R. downstream of LBG Base flows requirements in the Murrumbidgee >> To maintain and improve populations of platypus recognise that the Murrumbidgee has become an and other vertebrate fauna in Molonglo R. important source of water for contingency domestic downstream of LBG water supply, and will become an ongoing source of domestic supply. Within this large river, lower base >> Enhance native fish community (including BWS key flows can be accepted in the wetter months of the species) in Molonglo R. upstream and downstream year without significantly compromising the processes of LBG supporting aquatic ecosystems. In the winter months Base flows the absolute volumes are greater and consequently th In all months in all years the defined base flow is to a 90 percentile flow will still ensure that key riffle be protected. The base flow is defined as the 80th habitat is inundated and connectivity is provided. The percentile of stream flow unless another baseflow information supporting this approach for a differing regime is identified through specific assessment. In percentile for summer/winter flows in certain systems is addition, abstractions of surface water may never from research and experience in Victoria (Department exceed the flow rate. Abstraction of groundwater is for Natural Resources and Environment 2002). limited to 10% of the recharge rate to protect base flow.

44 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Flooding flows For urban lakes and ponds that were constructed Flooding flows, particularly channel maintenance before the year 2000 the nominal drawdown as a flows, are to be protected by restricting abstraction result of abstraction is 0.20m below spillway level. in water management areas to 10% of the flow This level of drawdown would result in the lake volume above the 80th percentile. The discharge most margins retreating approximately 2 metres in most critical at determining the width, depth and meander areas as pond design guidelines require edges to be frequency of channels is the 1.5 to 2.5 year annual sloped at approximately 1 in 10 for stability, safety recurrence interval flood event. and public health reasons. This drawdown limit had been established on the basis that those existing Specific conditions that can be placed on licenced lakes and ponds had been designed to fulfil their abstracters in relation to infrastructure limitations will ecological functions at operating at close to full supply also ensure that flooding flows of this magnitude are level. Historically it is noted that water level variations protected. without abstraction have been greater than 0.20m. Research on Canberra’s lakes and ponds indicates that NSW reaches with paramount rights drawdown to 0.60m is the upper limit without the risk for the ACT of adverse ecological effects increasing significantly. This group of reaches includes waters in NSW, over Exceeding this level may increase the risk of fish kills. which the Commonwealth has paramount rights to Therefore the drawdown caused by abstraction, of water for all the purposes of the Territory as a result of lakes and ponds constructed before 2000 can only the Commonwealth Seat of Government Acceptance Act exceed 0.20m if the activity is covered by intensive 1909. It includes the Queanbeyan River and its tributaries management and monitoring. For minor abstraction upstream of Googong Dam, and the Molonglo River and activities from lakes and ponds where management/ its tributaries in NSW including Jerrabomberra Creek. monitoring programs are uneconomical a drawdown Waters from the Queanbeyan River and tributaries of 0.20m provides an efficient and safe limit. entering the Googong Dam Area have been specifically For urban lakes and ponds constructed after 2000 developed for urban water supply purposes by the the maximum drawdown as a result of abstraction Googong Dam and associated infrastructure. Waters is 0.20m below spillway level, or a lower level if it can from the remaining NSW reaches in this category are be demonstrated that a pond has been explicitly important for existing or future Territory purposes designed to fulfil its required water quality and (as previously identified). The determination and ecological functions under the proposed drawdown maintenance of flow requirements in these waters to regime. As with other guidelines, there will be a need protect environmental values is the responsibility of to monitor the effect of this guideline on lake and NSW which has yet to specifically address this issue pond macrophytes and fish populations of stocked in these waters. However, to ensure protection of lakes over time. the Commonwealth rights to water under the Seat of Government Acceptance Act 1909 for all the purposes of Allow water level fluctuations of up to 0.60 m below the Territory, it is expected that water use be limited to full supply level to be consistent with natural seasonal that necessary to support stock and domestic purposes patterns, while continuing to protect waterbird breeding for traditional grazing enterprises and associated long habitat from drawdown during breeding season. established rural villages (or equivalent use). This is expected to ensure that adequate environmental flows Implementation into the ACT are maintained. Control of abstraction is seen as the appropriate mechanism for achieving environmental flows for Requirements applying to all modified these types of ecosystems. Total abstractions are ecosystems limited to the volume determined by these Guidelines, and detailed in the Water Resource Plan. During Impoundment drawdown levels low flow periods licensees would not be permitted Ponds and lakes sustain aquatic ecosystems within the to withdraw their entitlement except for stock waterbody, and protect downstream waters by removing and domestic purposes (as provided by the Water pollutants. An integral component of pond ecosystems Resources Act 2007). Conversely, during normal or high is the zone of macrophytes around the margin. flow periods abstraction of stormwater can play a Macrophytes provide habitat, stabilise and protect significant role in improving the ecological values of margins from wave action and assist with removal of modified ecosystems, as detailed in Section 2.5. pollutants. Macrophytes and their associated ecosystem components can be affected if a pond is drawn down The Guidelines do not require releases from lakes too far or for too long, compromising the ecological and ponds in modified ecosystems to maintain function of the pond. For this reason drawdown limits environmental flows in downstream waters. are set for urban lakes and ponds.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 45 The environmental flow requirements of the streams 5.4 URBAN ECOSYSTEMS downstream of impoundments are met through a combination of dam maintenance releases and water All streams, lakes and ponds within the urban area passing over the spillway. Although these waterbodies excluding the Molonglo River fall into this category. are commonly used for irrigation, this loss of water is There have been considerable changes to urban compensated by the augmented runoff coming from waterbodies as a result of urbanisation. Prior to urban catchments. European settlement, streams in the now urbanised part of the ACT, with the exception of the Molonglo Urban impoundments generally only have the capacity River, flowed only intermittently. Streams took the to release water by overtopping, or by discharge form of ‘chains of ponds’ where the stream was a set of through a valve at the base of the dam. Water in the ponds joined by a poorly defined streambed. Initially bottom of these reservoirs can be of a lower quality through land clearing, and more recently through the such that release of this water would potentially presence of impervious surfaces in urban areas, the compromise downstream aquatic ecosystems. It is urban streams now receive flows that exceed natural recommended that new dams be fitted with release flows. Additionally, urban stormwater can contain structures that allow water released from the dam to be large quantities of sediment, nutrients and pollutants. at temperatures that reflect natural inflow temperature. In recent years, there has been significant community The lake and pond water level requirement will be met support for restoring urban streams to a more natural principally by controls on abstraction. Abstraction condition. Introduction of water sensitive urban design from lakes and ponds will be permitted only if the in Canberra has led to installation of features such as water level was above the drawdown specified in these ponds, rain gardens, pervious pavements, bioswales Guidelines or in a watering plan developed for the and stormwater drains as more natural waterways and specific waterbody. on-site detention of stormwater. In 2013 management of Commonwealth water resources (including Lake Burley Griffin) in the ACT is under ACT Government management. The National Capital Authority has a Lake Burley Griffin Water Quality Management Plan (2011).

46 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 5.4 URBAN ECOSYSTEMS These Guidelines recommend that flows in urban Base flows streams be restored to natural flow regimes as far as In all months in all years the base flow is to be All streams, lakes and ponds within the urban area practicable, while recognising that it is unlikely that protected. The base flow is defined as the modelled excluding the Molonglo River fall into this category. streams will return to the pre-development ‘chain of natural 80th percentile of stream flow. In addition, There have been considerable changes to urban ponds’ condition. It should be noted that creeks in this abstractions of surface water may never exceed 10% waterbodies as a result of urbanisation. Prior to category were ephemeral prior to their catchment’s of the flow rate above the 80th percentile flow. European settlement, streams in the now urbanised urbanisation, hence assessment in comparison to Abstraction of groundwater is limited to 10% of the part of the ACT, with the exception of the Molonglo perennial creeks may not be appropriate. River, flowed only intermittently. Streams took the recharge rate to protect base flow. Ecological objectives form of ‘chains of ponds’ where the stream was a set of Flooding flows >> To maintain a range of healthy aquatic ecosystems ponds joined by a poorly defined streambed. Initially Flooding flows, particularly channel maintenance (all waterbodies) through land clearing, and more recently through the flows, are to be protected by restricting abstraction presence of impervious surfaces in urban areas, the >> To prevent degradation of downstream aquatic in water management areas to 10% of the flow urban streams now receive flows that exceed natural ecosystems through sediment deposition and high volume above the 80th percentile. The discharge most flows. Additionally, urban stormwater can contain flow rates (urban streams) critical at determining the width, depth and meander large quantities of sediment, nutrients and pollutants. >> To maintain healthy aquatic ecosystems in terms of frequency of channels is the 1.5 to 2.5 year annual In recent years, there has been significant community biota recurrence interval flood event. support for restoring urban streams to a more natural >> To maintain functional assemblages of Specific conditions that can be placed on licensed condition. Introduction of water sensitive urban design macrophytes in urban lakes, ponds and wetlands abstracters in relation to infrastructure limitations will in Canberra has led to installation of features such as >> To protect waterbird breeding habitat from also ensure that flooding flows of this magnitude are ponds, rain gardens, pervious pavements, bioswales protected. and stormwater drains as more natural waterways and drawdown during breeding season on-site detention of stormwater. >> To maintain populations of fish in urban Impoundment drawdown levels impoundments where stocking occurs To be consistent with 5.3.4

Implementation To be consistent with 5.3.4

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 47 6 MONITORING AND ASSESSMENT

48 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 6 MONITORING AND ASSESSMENT

A monitoring and assessment program is needed to confirm the flow requirements of local aquatic biota and ecological processes, and to determine if the indicators and ecological objectives nominated in the guidelines are the most appropriate for individual waterbodies. Using this information to refine the environmental flows is integral to the holistic approach used to develop these guidelines. Understanding the environmental flow requirements for rivers in the ACT, as elsewhere in Australia, is not a straightforward task. In Australia, we cannot rely on understanding gained from the very different northern hemisphere ecosystems. Australian streams have much more variable flow regimes than those in most other regions of the world. Understanding the effect of daily, seasonal, and event based flow variability to the long-term health of aquatic ecosystems is of great importance, but also presents a significant challenge. There is a considerable amount of research currently being undertaken into environmental flows in the Australian context, including work being conducted locally. The monitoring and assessment program will continue to build on this work. The monitoring and assessment program will also review the appropriateness of the ecological objectives and indicators identified in Section 4, and evaluate the effectiveness of the environmental flows in maintaining these ecological objectives. In part, this assessment process will be based on a continuation of the licence based monitoring that occurs in water supply catchments, and on the ongoing biological and water quality monitoring program in other catchments. However, there are also knowledge gaps that are not covered by these programs, and additional research will need to occur if we to evaluate the effectiveness of these guidelines. Some knowledge gaps are identified in Appendix 3. The ACT Government aims to modify existing monitoring programs through its Integrated Water Monitoring Plan. It is recommended that the additional research required should be a collaborative effort with other agencies to consolidate research and monitoring requirements and available resources. The information gained from the monitoring programs, and additional research should be reviewed on a regular basis, and the findings used to guide adjustments to the different environmental flows, ecological objectives, and ecological indicators. This program will also allow us to refine our understanding of flow – biota relationships.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 49 As a guide for developing a comprehensive Other issues raised during this and previous environmental flows monitoring and assessment environmental flow reviews include: program, a framework has been adapted from >> Appendix 2 recommendations from the 2010 review Cottingham et al (2004) Environmental Flows of the EFG (2006); Monitoring and Assessment Framework. The framework can be applied to each of the different environmental >> Review of “Ecologically sustainability of modified flow requirements and ecological objectives, and is environmental flows in the Cotter River during outlined below: drought conditions January 2003- April 2004. Final Report August 2004” by Norris, Chester and Thoms 1. Define the information needed for each ecosystem (Chessman, 2004); and environmental flow component, over appropriate temporal and spatial scales. >> Need to strengthen analysis of data including statistics and trends; and 2. Define the conceptual understanding of flow- ecology relationships and the questions to be >> Need to review the reference sites used for AUSRivas tested as formalised as ecological objectives as in to ensure they represent natural ecosystems. Section 4. Determine if there is a relationship of populations to flows. Consider adoption of genus as the default 3. Select the ecological indicators to be tested as level of taxonomic resolution (Chessman, 2010). defined in Section 4 Consider if macroinvertebrates in urban areas could 4. Determine the study design, accounting for the use SIGNAL as well. SIGNAL is used by Waterwatch. specific flows, and ecological objectives and >> Need to ensure AusRivas sampling sites are indicators and location within each ecosystem, representative of the reach, especially downstream guided by the decision framework in Cottingham et of dams, the sampling sites should not be too close al 2004 to the dams. 5. Optimise study design for the size of the ecological >> Rapid Appraisal of Riparian Condition (RARC, Jansen response to be detected, and the temporal and et al, 2005) or other method to be developed which spatial extent of the sampling design. is better suited to the ACT’s upland zones. 6. Implement the study design, and >> The difference between fish threshold and recovery 7. Assess whether the environmental flows have met population indicators should be explored. For the specific objectives and review the conceptual example, the threshold may be fine for the understanding and hypothesis, and feed this back populations that are going well eg Blackfish and into the adaptive management process. Macquarie Perch pre the Enlarged Cotter Dam, but to improve populations from an impact, may In addition to Murray–Darling Basin water reforms require more stringent indicators. framework for evaluating progress (MDBA, 2014b) will be considered in developing the environmental flows monitoring and assessment program. 6.1 APPLYING THE FRAMEWORK The specific monitoring requirements and research TO THE DIFFERENT ECOSYSTEMS needs for each ecosystem type, and generic flow AND FLOW COMPONENTS components are outlined in more detail below and in the following sections: Water supply >> filamentous algae assessed using standardised In the water supply catchments, the significant collection and processing methods as per Norris et research that has taken place during 2000-2017 al (2004). (for example, Chester 2003; Norris et al 2004; and ECD references in the Bibliography) has enabled >> Macroinvertebrate assemblages assessed using environmental flows to be better targeted to achieve protocols in the ACT AUSRIVAS sampling and specific ecological outcomes. Given the extensive processing manual Nichols et al (2000). datasets that have now built over time, further work >> Sediment deposition using techniques as per is needed to formulate general relationships between Ecowise Environmental (2005). flow and flow responses in terms of the various ecological indicators of river health. The determination of such relationship will improve predictive ability for managing environmental flow releases under changing environmental circumstances. Monitoring of flows and the ecological indicators will continue and be used to refine environmental flows.

50 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Further information is particularly needed regarding Groundwater the flows needed to enhance Macquarie Perch Groundwater discharge is important in maintaining and Two-Spined Blackfish populations, including base flows in streams, it is not possible to rely solely requirements for spawning and survivorship of young on controls on surface water abstraction to protect of the year. Understanding these relationships will base flow requirements. Recent investigations have assist in adapting environmental flows to protect reported that increasing groundwater abstractions these threatened , and to evaluate the suitability above 10% of the volume of long term recharge are of the fish based ecological indicators. In addition, likely to increase the periods of low flow in rivers subsequent reviews of the indicators for Blackfish (Evans et al 2005 and Rassam et al 2010) and this is should consider the Jacobs (2017) report findings and likely to have a negative effect on biota (Barlowet al recommendations. The annual Fish Management Plan 2005). We know from the literature that such changes produced by Icon Water considers how water can be will affect macroinvertebrates, but it is likely that other optimally managed for positive fish outcomes. components including fish, macrophytes, and algae Previous versions of the Guidelines included ecological will also be affected. The investigations were desktop objectives for the Cotter River Frog. However, genetic studies, and further on-ground research was put in analyses suggest this frog is a colour morph of Litoria place to assist in the management of this resource. A nudidigitus, a widely distributed species (W. Osborne, program monitoring groundwater levels and rainfall Pers Comm 2017). The 2017 review of the 2013 recharge rates was in place throughout areas where Guidelines recommended that objectives specific to groundwater use is highest. Data used to quantify the Cotter River Frog be removed from the EFG. groundwater processes and assessment of safe groundwater volumes for abstraction is described in Modified and urban ecosystems ABARES (2013). While there is still a level of uncertainty associated with each of the techniques used, the The CRCFE review of the 1999 Guidelines and the consistency in the assessment outputs provides a level Hillman review of the 2006 Guidelines indicated a need of confidence in the results. for a monitoring and research program in the modified and urban ecosystems to assess the effectiveness of Future environmental flow considerations the environmental flows. The environmental flows Requirement for all river and major creek longitudinal monitoring and assessment approach outlined by waterway constraints to provide passage for listed Cottingham et al 2004 assumes that the role of the species of fish, and identifying the genetic stock of environmental flow in maintaining or improving the the listed species, are legislated for in the USA. There ecological condition of the river has been identified. is currently little support to create additional fish This is not the case for most aquatic ecosystems. passages at dams in the ACT, on the basis that there The evaluation of environmental flows outside the are more cost effective opportunities to assist listed water supply catchments is not a straightforward species. In addition, the Cotter River needs to be process as streams can be affected by many impacts, isolated from the Murrumbidgee River due to the EHN for example; flow regulation, water quality degradation, virus and carp, as does Googong from carp, although riparian vegetation change and land use change. The the latter may already have been compromised. environmental flows research challenge is to disentangle Urban dams are stocked and fish ladders at those these confounded effects so that the effectiveness dams would not necessarily provide access to good of the environmental flow regime can be assessed. A breeding sites. research program has not yet been developed, but areas Section 2.7 identifies possible impacts of climate recommended for consideration are: change which may affect macroinvertebrate >> Investigation of the effectiveness of the base monitoring. flows and flooding flows at protecting ecological objectives >> Review of the appropriateness of the ecological indicators in representing ecological outcomes. >> Refinement and elaboration of ecological objectives being maintained by environmental flows. >> Evaluation of the effectiveness of the drawdown limit of urban lakes and ponds at protecting their aquatic ecosystems.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 51 GLOSSARY AND BIBLIOGRAPHY

52 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES GLOSSARY AND BIBLIOGRAPHY

Abstracter An abstracter is a person or corporation that abstracts water from a waterway, impoundment or bore Abstraction Abstraction refers to the removal of water from a natural waterway, impoundment or bore, and includes diversion of water. Adaptive Management Adaptive management is the systematic process of continually improving management policies and practices by learning from the outcomes of operational programs Aquatic Ecosystem For the purposes of these guidelines, an aquatic ecosystem is an ecosystem in a river stream, lake or pond bounded by the riparian zone. Aquifer An aquifer is a layer of rock or soil that is permeable and has the capacity to contain groundwater Augmentation The addition of water to a stream or aquifer, from an anthropogenic process. Base flow Base flow is the flow in a waterway that occurs between runoff events. For ACT streams most base flow is a result of seepage of groundwater into the channel. Biota Biota is a general term describing the animal or plant life of an area. Channel Maintenance Flows Channel maintenance flows are flows necessary for maintenance of the channel structure Urban Ecosystem An urban ecosystem is an aquatic ecosystem that has been significantly altered by human activity. Discharge Discharge refers to the release of water from a detention structure into a waterway. Diversion See abstraction. Note that for licensing or allocation purposes, abstraction and diversion may differ but for impacts on ecosystems the terms are effectively the same. Drawdown Drawdown is the extent to which the water level of an impoundment has been reduced below the full supply level.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 53 Ecosystem Macrophytes An ecosystem is a biological community of interacting Macrophytes are large water plants. Emergent organisms and their physical environment. macrophytes are plants that are rooted in the riverbeds or lakebeds, and protrude through the water surface. Ephemeral Streams Submerged macrophytes are plants that are rooted in Ephemeral streams are waterways that do not flow the riverbeds or lakebeds, but may have both aquatic continuously. That is, they tend to flow for a relatively and aerial adapted stems, leaves and reproductive parts. short period of time, usually only days or weeks, after a storm event. Modified Ecosystem In the context of this document a modified ecosystem Flooding Flows is an aquatic ecosystem that has been somewhat Flooding Flows are flows of water after storm events. altered by direct or indirect human influence. Flow Regime Multi-level Off-takes Flow regime describes the pattern of flow that occurs Multi-level Off-takes are structures that allow the release in a stream and will include such components as low of a controlled quantity of water from a variety of depths flows and flood events. in an impoundment thus allowing water of a particular Flushing Flows quality i.e. temperature to be released or diverted. Flushing Flows are flows resulting from storm events Natural Ecosystems or specific releases from impoundments, and typically A natural ecosystem is an aquatic ecosystem in which comprise high flow rates of a relatively short duration there has been minimal human impact. that mobilise sediments and change other instream physical and chemical processes. Operational flexibility Operational flexibility refers to the ability to use Fractured Rock Aquifer existing infrastructure to manipulate flow or water A fractured rock aquifer is an aquifer in which level within a waterbody to achieve certain outcomes. groundwater is stored in cracks and joints in the Potential operational flexibilities include the timing, bedrock, and not within the rock itself. Fractured rock capacity of regulate the temperature of releases, aquifers tend to contain smaller volumes of water volume and water quality of flows. than alluvial or consolidated aquifers and transmit the water slowly. Percentile A percentile is a value between 0 and 100 that indicates Impoundment the proportion of measurements that fall above the An Impoundment is an artificial body of water created percentile value. In this document the range of stream by the building of a dam. In the Guidelines the term is flows are expressed in percentiles. The 80th percentile used interchangeably with reservoir. flow is the flow that is exceeded 80% of the time. Key species That is, it is those commonly occurring (low) levels of Species as defined under the Nature Conservation Act flow. The 50th percentile, or median is that flow that 2014 and DI2012-11. is exceeded only half of the time. Percentile flows are represented graphically in Figure 2.

FIGURE 2. A GRAPHICAL REPRESENTATION OF PERCENTILE FLOWS

54 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Planned Environmental Water (PEW) Stressed Stream Environmental water committed in a water plan A stressed stream is a stream that has endured a (e.g. the ACT’s Water Resource Plan) for achieving prolonged period of low flow. These conditions environmental outcomes are often detrimental to stream health in the short term yet are a necessary component of the flow Pool Maintenance Flows regime because they improve the resistance of local Pool Maintenance flows are flows of water necessary organisms to period of low flow or drought conditions. to keep pools clear of sediment A stressed stream may also refer to a stream that is Priority Ecosystem Function (PEF) suffering from pollution. An ecosystem function that can be managed with Sustainable Yield environmental water and fulfils at least one criterion Sustainable yield refers to the quantity of water that set out in Schedule 9 of the Murray-Darling Basin Plan may be diverted without having an adverse effect on Priority Environmental Asset (PEA) dependent ecosystems An environmental asset that can be managed with Urban Lake or Pond environmental water and fulfils at least one criterion Water Features listed in the Territory Plan defined as set out in Schedule 8 of the Murray-Darling Basin Plan public land (unless specifically excluded). Generally Riffle Maintenance Flows an urban lake or pond is an impoundment that was Riffle maintenance flows are flows of water, necessary constructed for the purposes of minimisation of peak to keep riffles clear of fine sediment but does not break storm flows, pollution control and recreation. The up armoured layer if one has formed in the riffle impoundment is connected to the stormwater system, does not occur on private property and does not Riparian Vegetation include the Jerrabomberra Wetlands. Riparian vegetation is vegetation growing on the banks of streams or rivers that is influenced by its proximity Water-dependent Biota to a body of water. Organisms that rely upon proximity to a waterbody for survival. They are typically biota that live within or Special Purpose Flows immediately adjacent to a waterbody. A special purpose flow refers to a particular flow regime that is required to meet a specified purpose. Water Supply Ecosystem For example, some fish require a relatively unique A water supply ecosystem is an ecosystem in a flow regime, in terms of flow and temperature, before catchment primarily sued for water supply. spawning is initiated. Water Use Restrictions Stratified Reservoir Water use restrictions are defined in regulations made A reservoir becomes stratified when the water forms under the Utilities Act. a layered structure, each layer having a distinct temperature and water quality.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 55 BIBLIOGRAPHY Arthington A.H. and Pusey B.J. (1993) In-stream flow management in Australia: Methods, deficiencies and ABARES (2013) ACT Groundwater recharge future directions. Australian Biologist 6(1): 52-60. assessment. Supplementary data collection and recharge determination for five sub-catchments in the Arthington A.H. (1998) Comparative evaluation of ACT, April 2006 to November 2010. environmental flow assessment techniques: Review of holistic methodologies. Occasional Paper 26/98, Land ACT Government (1997) Environment Protection Act and Water Resources Research and Development http://www.legislation.act.gov.au/a/1997-92/default. Corporation, Canberra, ACT. asp Arthington A.H., King J.M., O’Keeffe J.H., Bunn S.E., ACT Government (1999) 1999 Environmental Flow Day J.A., Pusey B.J., Bluhdorn D.R. and Tharme Guidelines R. (1992) Development of an holistic approach for ACT Government (2004) Think water, act water. assessing environmental flow requirements of riverine Volumes 1 to 3. ecosystems. In: Water Allocation of the Environment. (ed. by J.J. Pigram and B. Hooper), Proceedings of ACT Government (2006) Environmental Flow International Seminar and Workshop, pp. 69-76, Centre Guidelines 2006 for Water Policy research, University of New England, ACT Government (2007). Water Resources Act 2007 Armidale, NSW. http://www.legislation.act.gov.au/a/2007-19/default. Barlow, A., Norris, R., and Nichols, S., (2005) asp Ecological effects of reducing baseflows. Final Report ACT Government (2007). Ribbons of Life: ACT Aquatic to Environment ACT. Institute for Applied Ecology, Species and Riparian Zone conservation Strategy. University of Canberra, ACT. Action Plan No. 29. Department of Territory and Canberra Water Supply (Googong Dam) Act 1974 Municipal Services, Canberra. (Commonwealth) ACT Government (2008) The Territory Plan, Australian Chessman (2004) Review of “Ecologically sustainability Capital Territory Planning and Land Authority, of modified environmental flows in the Cotter River Canberra, http://www.legislation.act.gov.au/ni/2008- during drought conditions January 2003- April 2004. 27/current/default.asp Final Report August 2004” by Norris, Chester and Thoms. ACT Government (2013) Water Resources Environmental Flow Guidelines 2013, DI2013-44. Chessman (2010) Assessing effects of flow alteration on macroinvertebrate assemblages in Australian ACT Government (2013) The ACT Nature Conservation dryland rivers. (2010 55, 1780-1800. Strategy 2013-23. Environment and Sustainable Development Directorate. Chester, H., (2003). Dams and flow in the Cotter River: effects on instream trophic structure and benthic ACT Government (2014) Nature Conservation Act metabolism. Unpublished Honours Thesis, University http://www.legislation.act.gov.au/a/2014-59/default. of Canberra asp Commonwealth of Australia, National Strategy for ACT Government (2016). ACT climate change Ecologically Sustainable Development, Dec 1992, adaptation strategy: living with a warming climate AGPS. Environment and Planning Directorate, Canberra. Cottingham, P., Quinn, G., Norris, R., King, A., ACTEW (2004), An Assessment of the Need to Increase Chessman, B., and Marshall, C., (2004) Environmental the ACT’s Water Storage, December 2004, ACTEW flows monitoring and assessment framework, CRC Corporation Pty Ltd, Canberra Freshwater Ecology, Canberra ACTEW (2005) ACT Future Water Options Water Coysh, J.L., Nichols, S.J., Simpson, J.C., Norris, R.H., Resources Modelling Report – Volume 1, April 2005, Barmuta, L.A., Chessman, B.C., and Blackman, P., ACTEW Corporation Pty Ltd, Canberra (2000). Australian RIVer Assessment System (AUSRIVAS) ActewAGL (2011) ACT sub-catchment water balance National River Health Program Predictive Model Manual. calculations. Report for Think water, act water. Cooperative Research Centre for Freshwater Ecology, Building 15, University of Canberra, ACT, 2601 Alluvium (2017a) Development of Source models for the ACT, for the ACT Government. Alluvium (2017b) ACT Source model scenarios, for the ACT Government.

56 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Department of Natural Resources and Environment Hall D.N. (1989) Preliminary assessment of daily flows (2002). Recommendations for Sustainable Diversion required maintaining habitat for fish assemblages in Limits over Winterfill Periods in Unregulated Victorian the Latrobe, Thomson, Mitchell and Snowy Rivers, Catchments. Catchment and Water Division, Gippsland. Department of Conservation, Forests & Department for Natural Resources and Environment, Lands, Victoria. Tech. Rep. Ser. No. 85. East Melbourne Victoria. Hall D.N. (1991) Management Plan for Freshwater Dusting,A., Broadhurst, B., Nichols, S., and Dyer, F. Fishes in Major Gippsland Rivers: Water Resource (2017) Review of the ACT Water Resources Environmental Requirements. Department of Conservation, Forests & Flow Guidelines 2013. Final Report to ACT Government, Lands, Victoria. Technical. Report. Serial. No. 107. Institute for Applied Ecology, University of Canberra, Hillman, T. (2010). Review of the ACT Water Resources Canberra. Environmental Flow Guidelines 2006 and their Dyer, F., El Sawah, S., Lucena-Moya, P., Harrison, E., application 2006-2009. Report to Environment ACT, Croke, B., Tschierschke, A., Griffiths, R., Brawata, Canberra. R., Kath, J., Reynoldson, T. and Jakeman, A.J., Intergovernmental Agreement on the Environment (2013). Predicting water quality and ecological (1992) responses. National Climate Change Adaptation Research Facility, Gold Coast. Jacobs (2017) Review of the Two-spined Blackfish monitoring program, for Icon Water. Dyer, ElSawah, Croke, Griffiths, Harrison, Lucena- Moya, Jakeman (2014) The effects of climate change Jansen, Robertson, Thompson & Wilson (2005) Rapid on ecologically-relevant flow regime and water quality Appraisal of Riparian Condition. RIVER AND RIPARIAN attributes. Stochastic environmental research and risk LAND MANAGEMENT TECHNICAL GUIDELINE NUMBER assessment 28 (1), 67-82 4A Ecowise Environmental Pty Ltd (2005), Sediment King J. and Louw D. (1995) Development and use of removal by environmental flow release. Cotter River the building block methodology for instream flow between Bendora reservoir and Cotter reservoir; assessments in South Africa. Environmental Flow Bracks Hole, Swimming Hole, Spur Hole. A report to Assessment Techniques Seminar, Cooma, NSW, 22 June. ACTEW, March 2005, Ecowise Environmental Pty Ltd, Canberra King, J. M. and Tharme, R. E. (1994). Assessment of the instream flow incremental methodology and Ecologically Sustainable Development Steering initial development of alternative instream flow Committee, endorsed by the Council of Australian methodologies for South Africa. Water Research Governments (1992). The National Strategy for Commission Report No. 295/1/94. Water Research Ecologically Sustainable Development, December, 1992 Commission, Pretoria, South Africa. Environment Protection Act 1997 (Commonwealth) Kinhill (1988) Techniques for determining environmental water requirements - a review. Evans WR, BFW Croke, JL Ticehurst, B Schoettker Technical. Report. Serial. No. 40. and AJ Jakeman (2005). Sustainable Groundwater Yield Assessment Sullivans Sub-Catchment, ACT. Lavergne, S., Mouquet, N., Thuiller, W., and Ronce, O. iCAM Client Report for Environment ACT. Integrated (2010). Biodiversity and climate change: integrating Catchment Assessment and Management (iCAM) evolutionary and ecological responses of species and Centre, School of Resources, Environment and Society, communities. Annual Review of Ecology, Evolution, and The Australian National University, Canberra, Australia. Systematics, 41: 321-350. Florance AR (2013) Effects of land-use on the response of Lintermans, M. (2004) Monitoring Program to Assess stream macroinvertebrate communities to drought, fire the Effectiveness of Environmental Flows in the Cotter and flood disturbance in the Lower Cotter Catchment. and Queanbeyan rivers in 2003, and to assess the Honours thesis. Institute for Applied Ecology, impacts of the 2003-4 drought-flows on recruitment University of Canberra, Canberra. of Gadopsis bispinosus and Macquaria australasica. Report to ACTEW Corporation July 2004. Wildlife Fulton, C., Starrs, D., and M. Ruibal (2009) Distribution, Research and Monitoring, Environment ACT, Lyneham, abundance and habitat use in montane populations ACT, 43 p. of Murray River crayfish (Euastacus armatus). Report to the ACTEW Future Water Planning Program. Research Lintermans, M., and Osborne, W., (2002) Wet and Wild, School of Biology, Australian National University Field Guide to the freshwater animals of the Southern Tablelands and high country of the ACT and NSW, Environment ACT, Canberra

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 57 MDBA (2014a) Basin-wide environmental watering Seat of Government Acceptance Act 1909 strategy. (Commonwealth) MDBA (2014b) Murray–Darling Basin water reforms: Stevenson, R.J., (1996). Patterns of benthic algae in Framework for evaluating progress. aquatic ecosystems. Algal ecology: freshwater benthic ecosystems. R Jan Stevenson, R. Bothwell, M.I. and Morrongiello, J.R., Beatty, S., Bennett, J., Crook, D.A., Lowe, R. L., California, Academic Press Inc. Ikedife, D.N.E.N., Kennard, M., Kerezsy, A., Lintermans, M., McNeil, D.G., Pusey B. and Rayner, T. (2011). Climate Swales S. and Harris J.H. (1995). The expert- change and its implications for Australia’s freshwater panel assessment method (EPAM): A new tool for fish. Marine and Freshwater Research 62, 1082–1098. determining environmental flows in regulated rivers. In: Harper D.M. and Ferguson A.J.D. (Eds) The Ecological Nature Conservation Act 2014 www.legislation.act. Basis for River Management. Wiley Press, Oxford, pp. gov.au/a/2014-59/default.asp 125–135. Nichols et al (2000) ACT Sampling and Processing Enlarged Cotter Dam (ECD) fish research: Manual https://ausrivas.ewater.org.au/index.php/ manuals-a-datasheets?id=54 Lintermans, M. (2012) Managing potential impacts of reservoir enlargement on threatened Macquaria Norris, R., Chester, H., Thoms, M., (2004) Ecological australasica and Gadopsis bispinosus in southeastern sustainability of modified environmental flows in Australia. Endangered Species Research 16: 1-16. the Cotter River during drought condition January 2003-April 2004: Final Report August 2004, Cooperative Lintermans, M. (ed.) (2013). Using translocation to Research Centre for Freshwater Ecology, University of establish new populations of Macquarie perch, Trout Canberra, Canberra 2601 cod and Two-spined blackfish in the Canberra region. Final report to ACTEW Water. Institute for Applied Ogden, R., Davies P., Rennie, B., Mugodo, J., and Ecology, University of Canberra, Canberra. Cottingham, P., (2004) Review of the 1999 ACT Environmental Flow Guidelines: A Report by the CRCFE Lintermans, M., Broadhurst, B. Thiem, J. D., Ebner, to Environment ACT, November 2004. B. C., Wright, D., Clear, R., and Norris, R. H. (2010). Constructed homes for threatened fishes in the Peat, M. S., and Norris, R. H. (2007). Adaptive Cotter River catchment: Phase 2 final report. Report management for determining environmental flows in to ACTEW Corporation. Institute for Applied Ecology, the Australian Capital Territory. In Proceedings of the 5th University of Canberra, Canberra. 205 p. Australian Stream Management Conference. Australian Rivers: Making a Difference (Eds. A. L. Wilson, R. L. Lintermans M., Broadhurst B., Clear, R. (2011). Dehaan, R. J. Watts, K. J. Page, K. H. Bowmer, and A. Characterising potential predation of Macquarie Curtis) pp. 312-317. perch Macquaria australasica by cormorants in Cotter Reservoir. Report to Bulk Water Alliance. Institute for Peat M., Moon K, Dyer F, Johnson, Briggs S V and Applied Ecology, University of Canberra, Canberra Nichols S J (2017). Creating institutional flexibility for adaptive water management: insights from two Broadhurst, B. T., Clear, R. C., Fulton, C. and management agencies. Journal of Environmental Lintermans, M. (2016). Enlarged Cotter Reservoir Management. 202: 188-197 ecological monitoring program: technical report 2016. Institute for Applied Ecology, University of Canberra, Prober, S. M., Williams, K. J., Harwood, T. D., Doerr, Canberra. V. A. J., Jeanneret, T., Manion, G., and Ferrier, S. (2015). Helping biodiversity adapt: supporting climate- Broadhurst, B. T., Ebner, B. C., Lintermans, M., Thiem, J. adaptation planning using a community-level modelling D. and Clear, R. C. (2013). ‘Jailbreak: A fishway releases approach. CSIRO Land and Water Flagship, Canberra. the endangered Macquarie perch from confinement below an anthropogenic barrier’ Marine and Rassam, D., Gilfedder, M., and Walker. G. (2010) Freshwater Research 64: 900-908. Assessing the impacts of groundwater development on low flows in rivers using resource indicators. Dennis, L.P., Broadhurst, B.T. and Lintermans, M., National Groundwater Conference, Canberra (2016). An accurate tool for ageing Two-spined November 2010. Blackfish for use in determining timing of spawning in upland streams in the Brindabella ranges, ACT, Reiser D.W., Ramey M.P., Beck S., Lambert T.R. and Australia. Ecological Management & Restoration, 17(1): Geary R.E. (1989) Flushing flow recommendations for 70-80. maintenance of salmonid spawning gravels in a steep, regulated stream. Regulated Rivers: Research and Ebner B, Lintermans M (2007) ‘Fish passage, movement Management, 3, 267-275. requirements and habitat use for Macquarie perch.’ Final Report to the Department of Agriculture,

58 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Fisheries and Forestry Australia. Parks, Conservation and Lands, Canberra. Ebner, B.C., Lintermans, M., and Dunford, M. (2011). A reservoir serves as refuge for adults of the endangered Macquarie perch. Lakes & Reservoirs: Research and Management 16: 23–33. Farrington, L.W., Lintermans, M. and Ebner, B.C (2014). Characterising genetic diversity and effective population size in one reservoir and two riverine populations of the threatened Macquarie Perch. Conservation Genetics 15: 707-716 Pavlova, A., Beheregaray, L. B., Coleman, R., Gilligan, D. M., Harrisson, K. A., Ingram, B. A., Kearns, J., Lamb, A. M., Lintermans, M., Lyon, J., Nguyen, T., Sasaki, M., Tonkin, Z., Yen, J. D. L. & Sunnucks, P. (2017). Severe consequences of habitat fragmentation on genetic diversity of an endangered Australian : a call for assisted gene flow. Evolutionary Applications, 10(6): 531-550. MacDonald, A.J., Young, M.J., Lintermans, M. and Sarre, S.D. (2014). Primers for detection of Macquarie perch from environmental and trace DNA samples. Starrs, D., Ebner, B.C., Lintermans, M. and Fulton, C.J. (2011). Using sprint swimming performance to predict upstream passage of the endangered Macquarie perch

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 59 APPENDICES

60 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES APPENDICES

APPENDIX 1: SCIENTIFIC BASIS FOR RECOMMENDATIONS FROM 2004 REVIEW OF THE ENVIRONMENTAL FLOW GUIDELINES (1999) The following text is extracted from the 2004 review of the ACT’s Environmental Flow Guidelines (1999) (Ogden et al. 2004). It presents the scientific basis for the ecological objectives set in the subsequent 2006 Guidelines. Those objectives are near identical to those reproduced in the 2013 Guidelines.

Science underpinning draft objectives The science underpinning the ecological objectives, and the environmental flows to achieve them, is summarised here. The environmental flows information (in italics) has been surmised from a review of the literature.

Macquarie Perch The biology and status of Macquarie Perch in the ACT have been thoroughly reviewed in Lintermans (2002) and ACT Government (1999b). Macquarie Perch is a threatened species in the ACT and nationally. Key aspects of its biology related to flow, and potential environmental flows benefits, are: >> It releases eggs that lodge in riffle gravels and cobbles. It therefore requires clean riffle gravels for spawning. Flushing flows may be needed to remove fine surficial sediments (FSS). >> It prefers deep, rocky pools. Flushing flows that clear pools of sediment may be required if sedimentation events occur, e.g. as has happened following recent fires. >> It has difficulty passing through relatively low-level stream barriers. Environmental flows might be required to drown out barriers. >> It uses rising water temperatures as a cue for spawning, and cold bottom-water releases from dams inhibit spawning. Cold water releases should be minimised. Although recruitment is required to sustain the fish populations, the scientific basis is not well established for the size and composition of the catch specified in Table 3 for Macquarie Perch. If the objectives in Table 3 are adopted, monitoring and assessment should be undertaken to determine if these levels of recruitment are adequate, or exceeds that required for sustainability.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 61 Healthy Ecosystems — algae An over-dominance of filamentous algae has flow-on effects to macroinvertebrates (Allan 1995; Chester 2003) and fauna that feed on them (e.g. fish). In addition algal growth during periods of low flow can trap sediment and accumulate organic matter that can eventually degrade both water quality and physical habitat used by fish and invertebrates (Allan 1995, Norris et al. 2004a). Key aspects of algae related to flow, and potential environmental flows benefits, are: >> Natural flushing flows clean surface and interstices of sediment and prevent the build-up of filamentous algae (Allan 1995; Norris et al. 2004a). Flushing flows below dams may reduce the build-up of filamentous algae and FSS (e.g. Norris et al. 2004a). >> Constant flow levels (reduced flow variability) favour Two-spined Blackfish Leaf-green Tree Frog (Cotter River Form) shifts in the algal community to filamentous forms (Allan 1995, Norris et al. 2004a). Variation in low flows The Cotter River form of the Leaf-green Tree Frog The biology and status of Two-spined Blackfish in the below dams may reduce shifts to filamentous forms of (Litoria nudidigitus), known as the Cotter River Frog, is ACT have been thoroughly reviewed in Lintermans algae (e.g. Norris et al. 2004a). (1998, 2002) and ACT Government (1999a). Two-spined described by Gillespie and Osborne (1994). The Cotter River Frog is strikingly different from the rest of the Blackfish is a threatened species in the ACT. Key Healthy Ecosystems — fine surficial species (Osborne et al. 1994). As well, this population is aspects of its biology related to flow, and potential sediment (FSS) deposition environmental flows benefits, are: now apparently confined to the Cotter River upstream of Bendora Dam (Osborne unpublished). It is therefore The accumulation of fine surficial sediments in riffles >> It shelters in the interstices of boulder and cobble of considerable regional significance. Key aspects of its reduces the area of the where healthy riffle beds, and is suspected to lay adhesive eggs on biology related to flow, and potential environmental biofilm and macroinvertebrate communities can the underside of boulders or cobbles. Flushing flows flows benefits, are (also see Appendix C): develop (and provide food for fish). This problem has to keep the bed clear of sediment infill may enhance been particularly acute in the Cotter and adjacent the survival. >> It breeds in streamside pools (Hero and Gillespie catchments following the recent fires (e.g. Nelson 1993; Holloway 1997). Flooding of semi-detached >> It may use rising water temperatures as a cue for 2003, Norris et al. 2004a). Flushing flows are the key to streamside pools in spring may be needed to provide preventing the build-up of FSS (Norris et al. 2004a). spawning, so that cold bottom-water releases from breeding sites. dams might inhibit spawning. Cold water releases should be minimised. >> High stream flows during the warmer months are Healthy Ecosystems — channel form likely to impact upon riverine frog populations by Gross channel form (i.e. ‘channel types’) is influenced The comments about recruitment targets for flushing eggs and larvae downstream (Gillespie by a number of factors related to stream flow: stream Macquarie Perch apply equally to Two-spined Blackfish. and Hines 1999; Gillespie and Hollis 1996). As well, power, sediment supply, and the competence of channel trout are effective predators of the Cotter River Frog flows to move sand, gravel, cobbles and boulders (Young (Gillespie 2001) and may gain access to streamside et al. 2002). There are two main features of channel types pools during inundation. High stream flows (above in the ACT that it might be possible to manage using natural peaks and frequencies) should be minimised e-flows: (1) the burial of channels by sediments, often to during the period when eggs and tadpoles are present. several metres depth, and (2) channel incision.

62 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Healthy Ecosystems — algae The smothering of channels with sediments reduces habitat quality and the number and depth of refuges An over-dominance of filamentous algae has flow-on in streams (Bond and Lake 2004, in press). Sediment effects to macroinvertebrates (Allan 1995; Chester deposition may occur if flows are not sufficient 2003) and fauna that feed on them (e.g. fish). In to remove material introduced into streams. This addition algal growth during periods of low flow can situation is an extreme version of the problem of trap sediment and accumulate organic matter that can deposition of FSS, although the sediments may have eventually degrade both water quality and physical been mobilised as a result of land use rather than habitat used by fish and invertebrates (Allan 1995, fires (Scott 2001). As for FSS, flushing flows are the Norris et al. 2004a). Key aspects of algae related to key to sediment removal (see section 5.2), although flow, and potential environmental flows benefits, are: sediments brought in by flows from upstream may >> Natural flushing flows clean surface and interstices confound the ‘flushing’ effects of sediment removal. of sediment and prevent the build-up of filamentous Channel incision will mainly be an issue in valleys algae (Allan 1995; Norris et al. 2004a). Flushing flows where there is a degree of development, below dams may reduce the build-up of filamentous reflecting long-term (e.g. 1000+ years) sediment algae and FSS (e.g. Norris et al. 2004a). deposition; otherwise channels will not have >> Constant flow levels (reduced flow variability) favour sediments to be incised. Incised channels are usually shifts in the algal community to filamentous forms observed to have less bed sediments (although they (Allan 1995, Norris et al. 2004a). Variation in low flows may be partially filled with sand) and flatter profiles, below dams may reduce shifts to filamentous forms of representing more degraded habitat than unincised algae (e.g. Norris et al. 2004a). channels (Ralph Ogden pers. obs.). Channel incision is thought to be controlled in part by stream power Healthy Ecosystems — fine surficial (Watson et al. 2002). sediment (FSS) deposition There is therefore a risk that channels will be incised The accumulation of fine surficial sediments in riffles if flows are augmented by inflows from interbasin reduces the area of the stream bed where healthy transfers. ‘Environmental flows’ in such rivers should biofilm and macroinvertebrate communities can aim to allow transmission of extra water while develop (and provide food for fish). This problem has minimizing channel erosion and incision. been particularly acute in the Cotter and adjacent catchments following the recent fires (e.g. Nelson Potential environmental flows benefits are: 2003, Norris et al. 2004a). Flushing flows are the key to >> Flushing flows to help prevent smothering of pools preventing the build-up of FSS (Norris et al. 2004a). and riffles with sediments. Healthy Ecosystems — channel form In instances where inter-basin transfers may occur, restoring the flow to match the natural flow regime may Gross channel form (i.e. ‘channel types’) is influenced minimize impact of increased stream power (cf. DNRE by a number of factors related to stream flow: stream 2002). However, further investigation of this is needed. power, sediment supply, and the competence of channel flows to move sand, gravel, cobbles and boulders (Young et al. 2002). There are two main features of channel types in the ACT that it might be possible to manage using e-flows: (1) the burial of channels by sediments, often to several metres depth, and (2) channel incision.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 63 APPENDIX 2: RECOMMENDATIONS FROM 2010 REVIEW OF THE ENVIRONMENTAL FLOW GUIDELINES (2006)

The following text is extracted from the 2010 review Recommendation 2. Hydrological data should be of the ACT’s Environmental Flow Guidelines (2006) compiled in a form and timely manner that permits (Hillman 2010). It presents the major recommendations water managers to monitor progress towards from that review and was included in the 2013 compliance with the Guideline’s flow rules and adapt Guidelines as a separate section. management practise accordingly. This material should be available for audit in line with Government As part of the 2017 review (Dusting et al. 2017) it was practise and consideration should be given to noted of the 2010 review recommendations: providing a summary report of compliance with the “The first recommendation relates to the severe Guideline’s flow rules annually as part of the ACT Water drought conditions that preceded the 2010 review and Report. is not critical to the present revision of the EFG. The Recommendation 3. The performance monitoring recommendation relating to hydrological reporting program should be assessed with a view to more has been largely adopted into water management closely aligning it with the Ecological Objectives practices in the ACT, with Icon Water subject to and proposed indicators set out in the Guidelines. ongoing compliance reporting as a requirement of This should lead to concise summary reports of their Licence to Take Water. performance data against ecological objectives in the The issues addressed by the remaining 2010 review annual ACT Water Report. recommendations continue to be unresolved and Recommendation 4. Consideration should be were confronted again as part of the 2017 review. given to developing a program that investigates The adequacy of monitoring programs, particularly sediment dynamics in ACT streams, particularly those relating to sediments and macrophytes, remain deposition of sediment in key areas including known deficient. As far as possible, these issues were addressed breeding habitats for native fish. This will lead to the in the present review through the revision of ecological establishment of a long term monitoring program. objectives and indicators (see Table 2). However, the ability to set meaningful objectives or indicators was Recommendation 5 . Compliance and performance impeded in many reaches by a lack of baseline data.” monitoring should be undertaken to close the adaptive management cycle for urban lake drawdown 2.1.1 Advice on changes to guidelines and macrophyte maintenance. Where the volume of water potentially warrants the work, specific studies As part of the review of the 2006 Guidelines, assessment should be carried out that maps the bathymetry of a of the performance of the Guidelines and advice on lake and the distribution of macrophytes and, on the potential changes was received from eminent aquatic basis of conceptual models describing the provision ecologist Professor Terry Hillman. Professor Hillman’s of human (including water supply) and ecological recommendations’ are summarised below. services by the , develop a hydrological Recommendation 1. In the event that the delivery management plan that optimises those services. of environmental flows remains a challenge in the Execution of that management plan, and appropriate immediate future, specific investigations should be monitoring and evaluation, should, in time, form the aimed at assessing the state of resilience of native fish basis of revised environmental flow recommendations populations (incl. age structure and recruitment) and for that system. selected macroinvertebrates with a view to determining the need and nature of special flow arrangements.

64 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES APPENDIX 2: RECOMMENDATIONS FROM 2010 REVIEW OF THE APPENDIX 3: SCIENTIFIC BASIS FOR RECOMMENDATIONS FROM 2017 ENVIRONMENTAL FLOW GUIDELINES (2006) REVIEW OF THE ENVIRONMENTAL FLOW GUIDELINES (2013)

The following text is extracted from the 2017 review The four criteria applied by the ACT for identify of the ACT’s Environmental Flow Guidelines (2013) ecosystem function are: (Dusting et al. 2017). It presents the scientific basis 1. The ecosystem function supports the creation and for the ecological objectives recommended for maintenance of vital habitats and populations the revision of the 2017 Guidelines. In general, the information in the tables is not an exhaustive 2. The ecosystem function supports the description of each reach, but largely restricted to transportation and dilution of nutrients, organic information pertinent to environmental flow provision. matter and sediment The tables assess and revise, where necessary, the 3. The ecosystem function provides connections ecological values, objectives and flow requirements on along a watercourse (longitudinal connections) a reach by reach basis. 4. The ecosystem function provides connections Note: comments which have been subsequently across floodplains, adjacent wetlands and added to the extract from Dusting et al (2017), have billabongs (lateral connections) been annotated accordingly. In line with Basin Plan requirements, the ACT considers Priority environmental assets and priority that Priority Ecosystem Assets and Priority Ecosystem ecosystem functions Function are environmental assets or functions that can be managed with environmental water. Many of The Basin Plan requires that Priority Environmental the ACT’s important freshwater assets are located in Assets (PEAs) and Priority Ecological Functions (PEFs) conservation areas and environmental water can only are identified as part of the ACT Long Term Watering be managed by limiting or prohibiting extractions. Plan. The methods for formally identifying PEAs, PEFs The tables describing the recommended objectives for and their environmental watering requirements are reaches within the ACT includes the identification of detailed in the Basin Plan (Chapter 8, Part 5). PEAs and PEFs. The five criteria applied by the ACT for identifying ecosystem assets are: Basin-wide environmental watering strategy 1. The water-dependent ecosystem is formally The BWS builds on the Basin Plan and is designed recognised in international agreements or, with to assist managers of waterways in meeting the environmental watering, is capable of supporting environmental objectives of the Basin Plan. It details species listed in those agreements the expected ecosystem responses to environmental 2. The water-dependent ecosystem is natural or near- watering across the Murray-Darling Basin. The four natural, rare or unique components – river flows and connectivity, native vegetation, waterbirds and native fish – each have 3. The water-dependent ecosystem provides vital habitat specific environmental expected outcomes, some 4. Water-dependent ecosystems that support of which will necessitate the development of new Commonwealth, State or Territory listed threatened ecological objectives to be incorporated into the species or communities EFG. As a result, consideration of BWS outcomes is 5. The water-dependent ecosystem supports, or with incorporated into the following tables. As with the environmental watering is capable of supporting, identification of PEAs and PEFs, only those ecosystem significant biodiversity components that can be managed with environmental water are considered.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 65 Reaches upstream of impoundments

Upstream of Corin, including unregulated tributaries Information BWS* The reaches upstream of Corin Reservoir are Cotter River is identified as an important unregulated and have a natural flow regime and high environmental asset for native fish for: conservation value. These reaches occur within the >> Presence of threatened species; and ACT’s conservation estate. >> A site of other significance Ecological and other values Presence of significant water-dependent vegetation >> Near-pristine natural ecosystems including some (*Note that environmental water can only be managed in these highly valued /wetlands, such as Ginini Flats reaches by limiting/prohibiting extraction.) wetland complex >> High biodiversity values (including aquatic and Flow requirement riparian vegetation, frogs, fish, reptiles, birds, spiny 2013 EFG flows: crayfish and other aquatic invertebrates) >> No interruption to natural flows to achieve both conservation and water supply outcomes.1 PEA/PEF All wetland systems and unregulated tributaries meet Flow recommendations: at least two criteria for identification as a PEA under >> No change to current EFG. Continue to maintain MDB Plan Schedule 81. natural flow regime and water quality to maintain >> “Criterion 2: The water-dependent ecosystem is ecological values natural or near-natural, rare or unique” “Criterion 5: The water-dependent ecosystem supports … significant biodiversity”

Objectives Proposed indicators Monitoring 2013 EFG objectives: None identified. See note1 See note1 To maintain healthy aquatic ecosystems in all natural ecosystems No additional objectives identified 1. In the absence of options to actively manage e-flows for particular outcomes in this reach, indicators are of limited use. Instead, this reach may be monitored to establish reference condition.

Reaches upstream of Googong Reservoir Information PEA/PEF The ACT has no statutory responsibility for management NSW reaches, not within ACT jurisdiction. of the Googong Reservoir catchment (the Googong, BWS Tinderry and Burra subcatchments) to ensure NSW reaches, not within ACT jurisdiction. compliance with the Seat of Government Acceptance Act 1909, the ACT considers that any abstraction of natural Flow requirement flows should not be greater than that necessary to 2013 EFG flows: support best practice traditional grazing enterprises. >> No interruption to inflows except that necessary for stock and domestic purposes (as provided by the Ecological and other values Water Resources Act 1998) and that already provided >> Near-pristine natural ecosystems for at the time these guidelines are listed.* >> High biodiversity values (including aquatic and (*Note that environmental water can only be managed in these riparian vegetation, frogs, small-bodied fish, reaches by limiting/prohibiting extraction (in NSW). reptiles, birds, spiny crays and other aquatic invertebrates) Flow recommendations: >> No change to current requirements.

Objectives Proposed indicators Monitoring 2013 EFG objectives: None identified. See note1 See note1 To maintain healthy aquatic ecosystems in all natural ecosystems No additional objectives identified 1. In the absence of options to actively manage e-flows for particular outcomes in this reach, indicators are of limited use. Instead, this reach may be monitored to establish reference condition.

66 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Corin Reservoir Information Flow requirement Corin reservoir is primarily managed for water supply 2013 EFG flows: outcomes (though releases occur to comply with >> No interruption to natural flows to achieve both e-flow requirements downstream). conservation and water supply outcomes Ecological and other values Flow recommendations: >> Water supply >> Existing guideline relates to adjacent riverine Potential values (currently data deficient): sections and should be removed. >> Waterbirds >> Proposed flow guideline: reservoirs should be managed primarily for water supply, but >> Drought refuge complementary ecological benefits (such as >> Recruitment opportunity for Two-spined Blackfish drought refuge or refuge for an endangered species) should be sought within the bounds of operational PEA/PEF Does not meet the criteria for identification as a PEA or restrictions. PEF under MDB Plan Schedules 8 and 9 OPERATIONAL FLEXIBILITY BWS The water level in Corin Reservoir is a function of Presence of BWS key fish species (Two-spined Blackfish)* inflow, transfer for water management and urban water usage and e-flow requirements downstream. In (*Cormorants are present in Cotter River reaches, but their presence a scenario of high water usage and low inflow, there is discouraged due to their predation on Macquarie Perch (a is the potential for a relatively fast drop in water level. threatened species) in Cotter Reservoir. Additionally, environmental flows are unlikely to influence waterbirds in this reach.) This is considered outside the control of Icon Water.

Objectives Proposed indicators Monitoring

2013 EFG objectives: None identified. See See notes1,2 To maintain healthy aquatic ecosystems notes1,2

Additional objectives: 1 fish per net night3 Bi-ennial, 10 fyke net To maintain populations of Two-spined Blackfish nights • Baseline information regarding waterbird composition and abundance in this reach. (Priority B) • How significantly do flow releases affect water levels in Corin Reservoir? (Priority B) • Potential impacts of fluctuating water levels on Two-spined Blackfish recruitment and growth (Priority B) • Baseline for Two-spined Blackfish population needs correlation with flows (Priority A) Added by ACT Govt, also to be added to other Cotter reservoirs and reaches where applicable, also see Corin dam to Bendora reach note 3. Notes 1. There is limited capacity to manage water levels for ecological outcomes in Corin Reservoir. Thus, indicators are not included, except for Two- spined Blackfish, which is a BWS-listed species. 2. Cormorants are present in Cotter River reaches, but their presence is discouraged due to their predation on Macquarie Perch (a threatened species) in Cotter Reservoir. Additionally, environmental flows are unlikely to influence waterbirds in this reach. 3. The indicator is targeted at detection of the population. There is no robust method for reliable detection of young of the year, thus a related indicator is not appropriate.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 67 Googong Reservoir Information Flow requirement Googong Reservoir is primarily managed for water 2013 EFG flows: supply outcomes (though releases occur to comply >> No interruption to natural flows to achieve both with e-flow requirements downstream). conservation and water supply outcomes Ecological and other values Flow recommendations: >> Water supply >> Existing guideline relates to adjacent riverine >> Recreation sections and should be removed. >> Fish community free of carp >> Proposed flow guideline: reservoirs should >> Water quality be managed primarily for water supply, but complementary ecological benefits (such as drought PEA/PEF refuge or refuge for an endangered species) should be Does not meet the criteria for identification as a PEA or sought within the bounds of operational restrictions PEF under MDB Plan Schedules 8 and 9

BWS Does not meet criteria for consideration* (*While there are BWS key species present in Googong Reservoir (eg Silver Perch), they are not self-sustaining populations and their on-going persistence is a result of recreational stocking rather than response to water management)

Objectives Proposed indicators Monitoring

2013 EFG objectives: None identified. See notes2 See notes2 To maintain healthy aquatic ecosystems No additional objectives identified1 Notes 1. While there are BWS key species present in Googong Reservoir (eg Silver Perch), they are not self-sustaining populations and their on-going persistence is a result of recreational stocking rather than response to water management 2. There is limited capacity to manage e-flows for ecological outcomes in Googong Reservoir. Thus, indicators are not included.

68 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Reaches between impoundments

Corin Dam to Bendora Reservoir, Bendora Dam to Cotter Reservoir Information Drought rules (stage 1): The reaches between impoundments on the Cotter >> Base flows: an average of 40 ML/day, or 75% of the system are located within the conservation estate 80th percentile or natural inflow whichever is the and the only impact is to the flow regime through the lesser volume. use of water to supply the ACT’s water. Note that the >> Riffle maintenance flow: 150 ML/day for three reservoirs are treated as separate reaches. consecutive days, every two months Ecological and other values >> Pool maintenance flow: >550ML/day for two Corin to Bendora: consecutive days between mid July and mid >> Diversity of fauna (including reptiles, platypus, water October rats, frogs, fish, invertebrates) Drought rules (stage 2): >> Intact riparian and aquatic vegetation >> Base flows: an average of 20 ML/day, with license >> Water delivery to water supply reservoirs requirements ensuring a scheme of variable low flow releases around the average of the daily base flow. Potential values (currently data deficient): >> Riffle maintenance flow: 150 ML/day for three >> Waterbirds consecutive days, every two months >> Pool maintenance flow: >550ML/day for two Bendora to Cotter: consecutive days between mid July and mid >> Diversity of fauna (including reptiles, platypus, water October rats, frogs, fish, invertebrates) Flow recommendations* >> Intact riparian and aquatic vegetation >> In lieu of scientific evidence suggesting adverse >> Water delivery to water supply reservoirs impacts of current flow requirements, guidelines should be retained. Maintain natural temperature PEA/PEF regime, leaving minimum requirements as per 2013 These reaches meet at least one criterion for EFG identification as a PEA under MDB Plan Schedule 8 because of the biodiversity of fauna: >> It is recommended that weekly variation in flows be reduced (from 50% to 25%) during Macquarie Perch >> “Criterion 5: The water-dependent ecosystem breeding season (October – December inclusive, supports, or with environmental watering is capable Bendora Dam to Cotter Reservoir). of supporting, significant biodiversity” >> Special purpose flows may be necessary to facilitate BWS Macquarie Perch spawning in the Bendora Dam to Cotter River is identified as an important Cotter Reservoir reach environmental asset for native fish for: (*See EFG Section 3 for details on calculation of recommended >> Presence of threatened species; and flow volumes)

>> A site of other significance OPERATIONAL FLEXIBILITY Presence of BWS key fish species (Two-spined Release valves at both Corin and Bendora dams are Blackfish, Macquarie Perch) manually controlled, requiring operators to travel to the dams (via roads potentially closed due to snow and Presence of significant water-dependent vegetation other weather conditions). These factors make step-up Flow requirement or step-down of flows difficult in practice, at least on a 2013 EFG flows: more frequent basis than weekly. Automation would be beneficial but would involve large capital expense. >> Base flows: 75% of the 80th percentile or inflows whichever is less Corin to Bendora >> Riffle maintenance flow: 150 ML/day for three Ideally, riffle maintenance flows should not occur consecutive days, every two months if temperature of released water is too low for fish >> Pool maintenance flow: >550ML/day for two breeding. For fish outcomes, the quality of the water consecutive days between mid July and mid released is potentially more influential than quantity. October Icon Water endeavour to match water quality to that of the natural inflow where this is practical within the constraints of the infrastructure and the primary water supply objective.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 69 Bendora to Cotter There is flexibility in timing of e-flow releases to Abstraction at Bendora Dam occurs at water supply allow for requirements of Macquarie Perch breeding. level only (offtake height is dependent on water quality This is adequately managed through an adaptive suitable for treatment plant). Timing and volume management process relating to the Cotter Reservoir needs to be flexible for water supply. Fish Management Plan (implemented by Icon Water). As in above reach, temperature of flows is important. The release valve at Bendora Dam can be operated at up to 375 ML/day (the safe operating capacity of the pipe), however the recommended maximum operating capacity is 250 ML/day (to minimise erosion of the bank opposite the outlet).

Objectives1 Proposed indicators Monitoring

2013 EFG objectives: Young of the year and year 1+ age classes (<120 mm) Annual sampling. EFTAG to further To maintain populations of Two- comprise >30% of the monitoring catch; AND catch is consider details – e.g. timing, sites spined Blackfish (both reaches) >2 fish for 75% samples (30 m section) in each reach and effort. across 2 sampling years2

To maintain populations of Recruitment detected at 75% of sites3. Minimum Annual sampling of 12 net nights per Macquarie Perch (Bendora Dam to capture of 1 Macquarie Perch (< 150 mm) per net site, 5 sites between Bendora Dam Cotter Reservoir) night4. and Cotter Reservoir5.

To maintain healthy aquatic Macroinvertebrate assemblage (AUSRIVAS Band A) Maintain current monitoring and ecosystems (both reaches) Non-dominance (<20% cover) of filamentous algae in reporting riffles6 Temperature, turbidity and DO mimic natural inflows Instream macrophyte cover <20%7

To prevent degradation of Sediment deposition is limited to <20% of total depth Currently not monitored or reported8. riverine habitat through sediment of pools at base flow Five yearly monitoring and reporting deposition (both reaches) recommended. • Riparian/macrophyte – flow relationships. Ability of e-flows to prevent encroachment in these reaches (B) • Riparian and macrophyte baseline condition in these reaches (B) • There are considerable knowledge gaps downstream of Corin Dam, particularly around effects of reversed seasonality (e.g. on Two-spined Blackfish). If periods of low flow are possible (e.g. Jan – April) it is not clear what this would achieve on various time scales (B) • Water level in Bendora Reservoir that leads to stranding of Two-spined Blackfish eggs (B) Notes 1. The 2013 EFG refer to an objective for Cotter River Frog, however, genetic analyses suggest it is a colour morph of Litoria nudidigitus, a widely distributed species of frog (W. Osborne, Pers Comm 2017). We recommend that objectives specific to the Cotter River Frog are removed from the EFG. 2. There has been considerable debate around the detail of this indicator, during the workshops and in subsequent feedback. Additionally, a concurrent review of the Two-spined Blackfish monitoring program did not make independent recommendations for biological indicators (Hale and Treadwell 2017). This suggests a lack of evidence to inform indicator parameters. As a result, EFTAG may wish to further revise the indicator as part of the revised EFG. Indicator could be adjusted according to catch at reference sites. The proposed indicator is based on means obtained from reference sites (see Appendix 1); they are reasonably conservative because of large standard deviation from the mean. The site criterion (75% across 2 years) is selected to account for there only being large standard deviation from catch mean. Without this measure, the indicator threshold would often be triggered as a result of limited sampling (rather than ecological factors). 3. The Macquarie Perch population is expanding upstream, but is currently small in this reach. Fyke nets are inappropriate for sampling the adult population, so instead the proposed indicator targets population recruitment. Adult population is somewhat inferred by recruitment. 4. Considerable variation in catch size means a presence/absence indicator is most appropriate in lieu of increased sampling. 5. Annual sampling is appropriate because of expanding distribution. Monitoring details are consistent with current sampling. 6. The 2013 EFG refer to non-dominance of filamentous algae 95% of the time, without clarification of temporal component. It is recommended that the “95% of the time” is removed and that it is stipulated in monitoring requirements that if filamentous algae are found to constitute >20% cover that more intensive sampling takes place. 7. It is assumed that flows of the magnitudes to prevent encroachment predominantly occur naturally in these reaches (in part because of limitations on dam release infrastructure). There is a knowledge gap around ability of e-flows to prevent encroachment in these reaches. 8. The greatest risk of sediment deposition in the pools of the Cotter River occurred following the 2003 fires during the drought. Rainfall had mobilised sediment from the burnt catchment to the river and there were not sufficient in-stream flows to transport the sediment through the system. Monitoring of pools was undertaken in the years immediately following the fires. The catchment has subsequently stabilised but we lack information about the volumes of sediment stored in pools, the extent or consequences of infilling, and the effectiveness of the pool maintenance flows. The 2012 and 2016 floods were observed to have worked the river channels and pools and some morphological changes had taken place. It is recommended that monitoring of the pools be undertaken once within each EFG period to determine the effectiveness of the flow regimes at maintaining pool depths. There is an opportunity to record observations of pool sediments when fish monitoring is undertaken (qualitative data) more frequently and would provide a useful input to the adaptive management process.

70 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Bendora and Cotter Reservoirs Information >> Water level in Cotter Reservoir is partly determined Bendora and Cotter reservoirs are primarily managed according to the Enlarged Cotter Dam Fish for water supply outcomes (though releases occur to Management Plan and informed by EFTAG. comply with e-flow requirements downstream). OPERATIONAL FLEXIBILITY Ecological and other values Bendora Reservoir >> Fish (Two-spined Blackfish, Trout Cod, Macquarie Water level is primarily a function of water supply Perch) needs. The reservoir water level is kept relatively stable >> Waterbirds (approx. 775 m) and while it can change because >> Water supply of maintenance and access requirements, there is minimal chance of it becoming so low as to have a Potential values (currently data deficient): major ecological impact. However, the rate of change >> Drought refuge in water level may be significant. For example, there is a risk of Two-spined Blackfish or Trout Cod eggs being PEA/PEF stranded if there is a rapid fall in water level during Does not meet the criteria for identification as a PEA or breeding season. As a result, reduction in water level PEF under MDB Plan Schedules 8 and 9 should be avoided in this period (mid-November), as BWS far as practicable considering the primary function of Presence of BWS key fish species (Two-spined the reservoir. Blackfish, Macquarie Perch, Trout Cod) Cotter Reservoir Flow requirement Large releases are now required in the enlarged Cotter 2013 EFG flows: See flow requirements for adjacent Reservoir before water level is substantially effected. riverine reaches, these define inputs. The addition of rock reefs has reduced impact of water Flow recommendations: level fluctuation on fish. The annual Fish Management Plan produced by Icon Water considers how water can >> Proposed flow guideline: reservoirs should be optimally managed for positive fish outcomes. be managed primarily for water supply, but complementary ecological benefits (such as drought refuge or refuge for an endangered species) should be sought within the bounds of operational restrictions

Objectives1,2 Proposed indicators Monitoring

2013 EFG objectives (for adjacent riverine reaches): Minimum 2 post-juvenile Two- Biennial sampling. EFTAG fish 1 To maintain populations of Two-spined Blackfish spined Blackfish per net night group to further consider details – (Bendora Res.) e.g. timing, location, net number.

To maintain populations of Macquarie Perch (Cotter Res.) Minimum total catch 3 Macquarie Annual sampling of 60 fyke net Perch per net night, comprised of nights3. > 50% individuals <150 mm.2

To maintain healthy aquatic ecosystems (both reservoirs) None identified4,5

Additional objectives: None identified6 To maintain populations of Trout Cod (Bendora Res.)

• Baseline information regarding waterbird composition and abundance in these reaches (B). • Impact of fluctuating water levels on Two-spined Blackfish and Trout Cod recruitment (B). • Two-spined Blackfish population condition and recruitment considered “good” for Bendora Reservoir (B). • Location of Trout Cod spawning and what role Bendora Reservoir might play (B). Notes 1. Mean Two-spined Blackfish per net night in Bendora Res. in sampling since 2001 is 9.27 (±7.3 SD; see Appendix 1). Given the large standard deviation from the mean, it is worth being conservative. Small sample size and large SD mean gives limited power for detecting trend. ACT Govt: noting that 2001 to 2009 was a period of extreme fire and drought; while 2010 to 2016 was more representative of average conditions. 2. See Appendix 1 for relevant data. 3. Increased frequency (annual) and intensity (60 nets) of sampling since previous guidelines to be commensurate with the increase in shoreline of the enlarged Cotter Reservoir. 4. There is limited capacity to manage water levels for ecological outcomes in both reservoirs. Thus, indicators are not included, except for populations of threatened fish, where possible. 5. Cormorants are present in Cotter River reaches, but their presence is discouraged due to their predation on Macquarie Perch (a threatened species) in Cotter Reservoir. Additionally, environmental flows are unlikely to influence waterbirds in this reach. 6. Knowledge gaps are too broad to devise meaningful indicators for Trout Cod in Bendora Reservoir. DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 71 Reaches downstream of impoundments Information >> Riffle maintenance flow: 100 ML/day for one day to Downstream of Cotter Dam and downstream of occur every two months Googong Dam. >> No pool maintenance flows required. Ecological and other values >> No specific drought flows are provided Downstream of Cotter Dam: Flow recommendations* >> Recreation Downstream of Cotter Dam: >> Connectivity (Murrumbidgee R. to Paddys R.) >> Incorporate flow variability and seasonal patterns >> Riparian vegetation (patches in good condition) into base flow in a manner consistent with other reaches below impoundments >> Ecosystem function >> Base flows: 75% of the 80th percentile (calculated • Major tributary to the Murrumbidgee R. monthly) or inflows whichever is less • Sediment transportation >> Riffle maintenance flows made up of 25% of the 80th • Prevent encroachment percentile (calculated monthly) delivered over 2-3 • Good water quality to maintain functioning days every month. ecosystem >> Drought flow provisions to be developed Downstream of Googong Dam: Downstream of Googong Dam: >> Dilution of flows heading into LBG >> Incorporate flow variability and seasonal patterns >> Riparian vegetation (patches in good condition) into base flow in a manner consistent with other reaches below impoundments >> Vertebrate fauna (platypus, water rats, reptiles) >> Base flows: 75% of the 80th percentile or inflows >> Irrigation supply whichever is less PEA/PEF >> Riffle maintenance flows made up of 25% of the 80th Does not meet the criteria for identification as a PEA or percentile (calculated monthly) delivered over 2-3 PEF under MDB Plan Schedules 8 and 9 days every month. >> Drought flow provisions to be developed BWS Cotter River is identified as an important (*See EFG Section 3 for details on calculation of recommended flows) environmental asset for native fish for: OPERATIONAL FLEXIBILITY >> Presence of threatened species; and Downstream of Googong >> A site of other significance There is potential to increase the volume of releases at Presence of significant water-dependent vegetation Googong Dam, which are currently at static low flow levels. This may increase releases from Lake Burley Flow requirement Griffin to the lower Molonglo River. 2013 EFG flows: The benefits of increasing e-flows would need to be >> Baseflows downstream of Cotter: 15 ML/day considered carefully. For example, fish in this reach are >> Baseflows downstream of Googong: 10 ML/day or from stocked populations and unlikely to respond to inflow whichever is less increases in e-flows.

72 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Reaches downstream of impoundments Objectives1 Proposed indicators Monitoring

2013 EFG objectives: Macroinvertebrate assemblage (AUSRIVAS Band A) Maintain current To maintain healthy aquatic Non-dominance (<20% cover) of filamentous algae in riffles2 monitoring and reporting2 ecosystems downstream of Cotter Temperature, turbidity and DO mimic natural inflows Dam

To maintain healthy aquatic Macroinvertebrate assemblage (AUSRIVAS Band A) Maintain current ecosystems downstream of Non-dominance (<20% cover) of filamentous algae in riffles2 monitoring and Googong Dam reporting2 Temperature, turbidity and DO mimic natural inflows

Additional objectives: Extent and condition of riparian vegetation is maintained or improved vegetation To maintain riparian vegetation condition and values downstream of Cotter Dam extent monitoring (5 yearly)

To maintain connectivity for None identified1,3 fish populations/habitats downstream of Cotter Dam • Seasonal patterns for both reaches – a requirement for determining base flows (A) • Flows required to allow fishway downstream of Cotter Dam to operate effectively and if releases from Cotter Dam are required to meet these flows (or is flow from Paddy’s River sufficient?) (B) • Providing higher flows downstream of Googong Dam has downstream consequences for Lake Burley Griffin and potentially the Molonglo River downstream of Lake Burley Griffin. The consequence of any increased flows to Lake Burley Griffin (see later table) for water quality need to be resolved before the recommendation can be implemented (A) Notes 1. The 2013 EFG contain fish-specific objectives downstream of Cotter Dam, it is recommended that these objectives be removed. While some BWS key fish species exist downstream of Cotter Dam, these are not self-recruiting populations. Flows should be targeted at supporting their survival through healthy aquatic ecosystems. 2. The 2013 EFG refer to non-dominance of filamentous algae 95% of the time, without clarification of temporal component. It is recommended that the “95% of the time” is removed and that it is stipulated in monitoring requirements that if filamentous algae is found to constitute >20% cover that more intensive sampling takes place. 3. There is a fishway in this reach, which dominates level of connectivity for fish (rather than e-flows). It is included here to align with BWS requirements regarding connectivity, but given limited response to e-flow, we do not recommend including it as an objective in the revised EFG.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 73 Natural Ecosystems

All reaches Information Flow requirement The reaches Natural Ecosystems are unregulated, have 2013 EFG flows: a natural flow regime and high conservation value. Baseflows are to be protected: Baseflow is defined as the modelled natural 80th percentile of stream flow. Ecological and other values >> Near-pristine natural ecosystems including some Abstractions of surface water may never exceed the highly valued bogs/wetlands flow rate. Abstraction of groundwater is limited to 10% >> High biodiversity values (including aquatic and of the recharge rate to protect base flow. Abstractions riparian vegetation, frogs, small-bodied fish, reptiles, should allow natural flow variability to be maintained. birds, spiny crays and other aquatic invertebrates) Flooding flows, particularly channel maintenance PEA/PEF flows, are to be protected by restricting abstraction in All reaches meet at least two criteria for identification water management areas to 10% of the flow volume as a PEA under MDB Plan Schedule 8: above the 80th percentile. The discharge most critical at determining the width, depth and meander >> “Criterion 2: The water-dependent ecosystem is frequency of channels is the 1.5 to 2.5 year annual natural or near-natural, rare or unique” recurrence interval flood event. >> “Criterion 5: The water-dependent ecosystem Flow recommendations: supports … significant biodiversity” No change to current requirements (abstraction limits BWS already in place). Continue to maintain natural flow Does not meet criteria for consideration1 regime and water quality to maintain an intact riparian zone/in-stream macrophytes

Objectives Proposed indicators 2013 EFG objectives: None identified. See note1 • To maintain healthy aquatic ecosystems in terms of biota • To prevent degradation of riverine habitat through sediment deposition Additional objectives: • To maintain high biodiversity values • To maintain riparian zone and in-stream macrophytes Notes 1. In the absence of options to actively manage e-flows for particular outcomes in this reach, indicators are of limited use. Instead, this reach may be monitored to establish reference condition for other reaches. The proposed objectives could be considered for future EFG reviews, however for now they can be folded under the broad objective of maintaining aquatic ecosystems. 2. ACT Govt: Climate change indicators are not related to eflows, but should be considered in future.

74 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Modified Ecosystems

Murrumbidgee River Information Flow requirement The environmental flow rules implemented in the 2013 EFG flows: NSW section of the Murrumbidgee upstream of the Baseflows: 80th percentile of stream flow November ACT are defined in the Snowy Water Inquiry Outcomes to May inclusive; 90th percentile of stream flow June to Implementation Deed (SWIOID 2002), and defined October inclusive annually based on inflows in the preceding year (NSW DPI 2017). Environmental flows from NSW In addition, abstractions of surface water may never upstream are currently not protected within NSW exceed the flow rate. and are likely to pass through the ACT unaffected by Abstraction of groundwater is limited to 10% of the activity in the ACT because they are not targeted or recharge rate to protect baseflow. accounted for in ACT planning. Flooding flows, particularly channel maintenance Ecological and other values flows, are protected by restricting abstraction >> Riparian vegetation activities to ensure that abstraction does not affect the frequency of channel maintenance events. The >> Habitat complexity and geomorphic value discharge most critical at determining the width, (wetlands, bedrock, gorges) depth and meander frequency of channels is the 1.5 >> Murray Cod (native), Trout Cod (descendents of to 2.5 year annual recurrence interval flood event. A conservation stockings) restriction of abstraction to flows below that threshold >> Other fauna (including a diversity of invertebrates, or a restriction on the rate of abstraction that can shield shrimp, raptors, reptiles) occur during those events, will ensure that channel maintenance flows occur at appropriate frequencies. >> Recreation Flow recommendations: >> Water supply >> No change to existing protected flows, though the >> Plant dispersal timing of abstractions could be stipulated where PEA/PEF ecologically important* The presence of threatened species (Murray Cod and >> Murrumbidgee to Cotter and Murrumbidgee to Trout Cod) means the Murrumbidgee River meets at Googong have restrictions on extractions, it was least one criterion for identification as a PEA under recommended these remain MDB Plan Schedule 8: >> Environmental flow releases downstream of >> “Criterion 4: Water-dependent ecosystems that Tantangara are protected from extraction through support Commonwealth, State or Territory listed the ACT threatened species or communities” (*Extraction in Murrumbidgee River can occur under drought BWS conditions. This may occur increasingly often under future Upland Murrumbidgee main channel is identified as an climates. This is not clearly stated in EFG, but is in Icon Water’s Licence to Take Water (WU67). It is recommended that the links important environmental asset for native fish for: between the EFG and other documents be clarified and made >> Key movement corridors, threatened species, and a explicit.) site of other significance Presence of BWS key fish species (eg Murray Cod)* Presence of significant water-dependent vegetation Presence of waterbirds

(*The BWS recommends ACT reaches of the Murrumbidgee River as candidate sites for the establishment of additional populations of Silver Perch. Silver Perch are functionally extinct within the ACT and the only way to establish additional populations in the ACT is to undertake a stocking program. This is outside the scope of the EFG.)

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 75 Objectives Proposed indicators Monitoring Other ACT reaches including Molonglo, Naas and Gudgenby rivers

2013 EFG objectives: Macroinvertebrate assemblage Continue existing To maintain healthy aquatic ecosystems in terms of biota (AUSRIVAS Band A) monitoring and 1 Non-dominance (<20% cover) of reporting filamentous algae in riffles1

To prevent degradation of riverine habitat through sediment None identified2 deposition

Additional objectives: None identified3 To maintain extent of water dependent fringing and in- channel native vegetation

To enhance native fish community, including Murray Cod Recruitment of Murray Cod detected at 75% EFTAG fish group and Murray River Crayfish sites in reach across 2 sampling years5,6 to consider details, Murray River Crayfish detected8 including timing, techniques and sites

To maintain diversity and increase abundance of waterbirds. None identified3,4

To maintain habitat complexity and geomorphic values None identified3 • Fish requirements for connectivity in the Murrumbidgee River. Promoting connectivity for fish is an objective of the BWS (B). • A number of native fish recruitment: flow relationships are unknown (B). • How the riparian vegetation along the Murrumbidgee River corridor (and particularly the long lived riparian species) are responding to the effects of Tantangara Dam (B). Notes 1. The 2013 EFG refer to non-dominance of filamentous algae 95% of the time, without clarification of temporal component. It is recommended that the “95% of the time” is removed and that it is stipulated in monitoring requirements that if filamentous algae is found to constitute >20% cover that more intensive sampling takes place 2. Sedimentation of the pools in the Murrumbidgee River is a function of historical land use activities and is unable to be influenced by the management of flows. Monitoring is therefore not relevant to EFG. 3. Under current flow releases from Tantangara Dam there is limited capacity to influence this proposed objective. It is assumed that there will be no changes to releases from Tantangara Dam in the next five years. Such scenarios expose the vulnerability of ACT ecosystems to extractions upstream, over which the ACT has little or no control. While this geomorphology objective is not recommended for the present EFG revision, it could be reconsidered during future reviews. 4. There is an absence of baseline data for waterbirds in this system, thus meaningful indicators could not be formulated. 5. The site criterion (75% across 2 years) is selected to account for methodological issues. Without this measure, the indicator threshold would potentially be triggered as a result of sampling issues (as opposed to an ecological issue). 6. The proposed indicator targets population recruitment on account of methodological issues with sampling adult population. Adult presence is somewhat inferred by recruitment. 7. Detection probability using existing methods is low for Murray River Crayfish. While presence/absence detection may be achievable, population estimates are unreliable.

76 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Other ACT reaches including Molonglo, Naas and Gudgenby rivers Information BWS Rivers, lakes and streams in the Modified Ecosystem Presence of BWS key fish species (Murray Cod) category include those water bodies outside Namadgi Presence of significant water-dependent vegetation National Park, Tidbinbilla Nature Reserve and the Presence of waterbirds Canberra urban area. The Molonglo River, and the Queanbeyan River upstream of Googong Reservoir Flow requirement are also considered Modified Ecosystems. These 2013 EFG flows: ecosystems have been modified by catchment activities including landscape change, and Baseflows are to be protected: Baseflow is defined as th modifications to the natural flow regime the modelled natural 80 percentile of stream flow Abstractions of surface water may never exceed the Ecological and other values flow rate.Abstraction of groundwater is limited to 10% All lakes: of the recharge rate to protect base flow >> Drought refuge Flooding flows, particularly channel maintenance Jerrabomberra Wetlands: flows, are to be protected by restricting abstraction in >> DIWA listed (since 1990s) for its waterbirds and water management areas to 10% of the flow volume geomorphological features above the 80th percentile. The discharge most critical at determining the width, depth and meander >> Biodiversity values (including macrophytes, turtles, frequency of channels is the 1.5 to 2.5 year annual platypus, dragonflies) recurrence interval flood event. Molonglo River downstream of LBG: Flow recommendations: >> Riparian vegetation (patches in good condition) >> Jerrabomberra Wetlands: >> Platypus, fish and other vertebrate fauna • Allow periodic drawdown* >> Recreation >> Molonglo Downstream LBG: Note that other values of this reach are recognised in • Maintain natural flow and temperature regime, the Molonglo Corridor Management Plan. where possible.** PEA/PEF (* Note that there is no capacity for actively managing flows in Jerrabomberra Wetlands. The high biodiversity values of Jerrabomberra Wetlands meet at least one criterion for identification **Note there is limited capacity for top releases from LBG) as a PEA under MDB Plan Schedule 8: OPERATIONAL FLEXIBILITY >> “Criterion 5: The water-dependent ecosystem The lower Molonglo (downstream of LBG) is the only supports … significant biodiversity” reach in this category with potential flexibility in flow delivery. This potential and related issues are discussed in the table pertaining to Lake Burley Griffin.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 77 Lake Burley Griffin

Objectives Proposed indicators Monitoring

2013 EFG objectives: Macroinvertebrate assemblage (AUSRIVAS Continue existing To maintain healthy aquatic ecosystems in terms of biota Band A) monitoring and 1 Non-dominance (<20% cover) of filamentous reporting algae in riffles1

To prevent degradation of riverine habitat through None identified2 sediment deposition

To maintain and improve functional assemblages of None identified4 macrophytes in modified lakes, ponds and wetlands3

Additional recommended objectives: None identified4 To maintain and improve riparian vegetation in Molonglo R. Downstream of LBG

To maintain and improve populations of platypus and None identified4 other vertebrate fauna in Molonglo R. Downstream of LBG

Enhance native fish community (including BWS key Upstream of LBG: Murray Cod present and EFTAG fish group species) in Molonglo R. Upstream and Downstream of LBG recruitment detected at 75% of sites across to consider details, 2 years5 including timing, Downstream of LBG: None identified5 techniques and sites • Limitations imposed by on fish population in Molonglo River downstream of LBG (B) • Response of fish populations to increased flows in Molonglo River downstream of LBG (A) • Baseline macrophyte assemblages in Modified Ecosystems (A) Notes 1. The 2013 EFG refer to non-dominance of filamentous algae 95% of the time, without clarification of temporal component. It is recommended that the “95% of the time” is removed and that it is stipulated in monitoring requirements that if filamentous algae is found to constitute >20% cover that more intensive sampling takes place. 2. Sedimentation of the pools in Modified Ecosystems is a function of historical land use activities and is unable to be influenced by the management of flows. Monitoring is therefore not relevant to EFG. 3. Amended from reference to “urban lakes and ponds” in 2013 EFG 4. Knowledge gaps are too broad to devise meaningful indicators for macrophytes in Modified Ecosystems. Additionally, there is limited potential to actively manage flows for in Modified Ecosystems (also see table pertaining to management of Lake Burley Griffin). 5. Releases from LBG to lower Molonglo are severely limited by infrastructure restrictions. This is unlikely to change in the next five years. As a result, specific indicators have not been identified for this reach. Objectives are not appropriate here at this time, though future review recommended by the ACT Govt: there is no evidence of Murray Cod spawning upstream of LBG, so the recruitment indicator should be deleted. 6. For the most part, large-bodied fish populations in the reach upstream of LBG are non-recruiting. They are typically fish stocked and lost from Googong Reservoir 7. The potential for maintaining waterbird populations at Jerrabomberra Wetlands was considered. This is unlikely to be achieved through e-flows in Jerrabomberra Wetlands. Additionally, any enhancement of waterbird population could threaten operational requirements of the nearby Canberra airport.

78 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Lake Burley Griffin Information Abstractions of surface water may never exceed the Lake Burley Griffin is managed according to a hierarchy flow rate. Abstraction of groundwater is limited to 10% of lake use values, as listed in the Lake Burley Griffin of the recharge rate to protect base flow Abstraction Guide (EPA 2014). The primary management Flooding flows, particularly channel maintenance goal for Lake Burley Griffin is for recreation. flows, are to be protected by restricting abstraction in Ecological and other values water management areas to 10% of the flow volume >> Recreation above the 80th percentile. The discharge most critical at determining the width, depth and meander >> National capital values frequency of channels is the 1.5 to 2.5 year annual >> Water quality and resources recurrence interval flood event. >> Tourism and commercial development Flow recommendations: Note that these values (except specific ecological values) are Allow water level fluctuations of up to 0.6 m below stipulated and ordered in the Lake Burley Griffin Abstraction Guide (EPA 2014). full supply level while continuing to protect waterbird breeding habitat during breeding season (drawdown >> Ecological limited to 0.2 m during July to November inclusively). • Vertebrate fauna (flying foxes, water rats, fish, platypus) OPERATIONAL FLEXIBILITY Water levels in LBG are tightly managed for purposes • Macrophytes other than ecological outcomes. The cost of top- • Silver gulls (on Spinaker Island) releases from Lake Burley Griffin is effectively prohibitive, • Diversity of waterbirds currently. Licencing requirements also prohibit LBG filling to the point of spilling. While the infrastructure permits >> Educational and scientific bottom-releases, flows are cold, turbid and low in DO. It is not known if such releases are ultimately beneficial PEA/PEF for biota. There are some unknowns relating to fish Does not meet the criteria for identification as a PEA or requirements in the downstream reach. PEF under MDB Plan Schedules 8 and 9. In terms of volume, it was suggested that current BWS outflow from LBG closely mimics natural inflow, with Presence of significant water-dependent vegetation water only retained to compensate for evaporation Presence of waterbirds loss (abstraction close to 1 GL, despite existing abstraction licences). Flow requirement 2013 EFG flows: The case for infrastructure alteration (e.g. thermal curtains) would be improved by greater understanding Baseflows are to be protected: Baseflow is defined as of flow-ecology relationships for the reach the modelled natural 80th percentile of stream flow. downstream of LBG.

Objectives Proposed indicators Monitoring

2013 EFG objectives: None identified1 To maintain healthy aquatic ecosystems in terms of biota

To maintain and improve functional assemblages Presence of emergent macrophytes of sufficient Littoral zone monitored of macrophytes density and diversity to perform beneficial WQ from aerial photos, processes and provide habitat for desired fauna. examining macrophyte Submerged macrophytes present at density that spatial extent over time, perform beneficial WQ processes species and colour.

Additional objectives: None identified2 To maintain diversity and abundance of waterbirds • Baseline survey data of waterbird diversity and abundance on Lake Burley Griffin (A) Notes 1. There is limited capacity to manage water levels for ecological outcomes in Lake Burley Griffin. Thus, indicators are not included, except for macrophytes, as per BWS requirements. 2. Knowledge gaps are too broad to devise meaningful indicators for waterbirds in Lake Burley Griffin.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 79 Wetlands Information Abstractions of surface water may never exceed the There are some important natural wetlands (such as flow rate. Horse Park wetland) that are threatened by urban Abstraction of groundwater is limited to 10% of the development altering the flow regime to the wetland. recharge rate to protect base flow Ecological and other values Flooding flows, particularly channel maintenance No specific values identified flows, are to be protected by restricting abstraction in water management areas to 10% of the flow PEA/PEF volume above the 80th percentile. The discharge most Does not meet the criteria for identification as a PEA or critical at determining the width, depth and meander PEF under MDB Plan Schedules 8 and 9. frequency of channels is the 1.5 to 2.5 year annual BWS recurrence interval flood event. Presence of significant water-dependent vegetation Flow recommendations: Presence of waterbirds Natural flow and water level regime remains unchanged in wetlands. In particular, protect wetlands Flow requirement from increased flows from urban areas. 2013 EFG flows: Baseflows are to be protected: Baseflow is defined as the modelled natural 80th percentile of stream flow

Objectives Proposed indicators Monitoring

2013 EFG objectives: None identified1 To maintain healthy aquatic ecosystems in terms of biota

To maintain functional assemblages Presence of emergent macrophytes of sufficient density Littoral zone monitored from of macrophytes in wetlands2 and diversity to perform beneficial WQ processes and aerial photos, examining No additional objectives were provide habitat for desired fauna. macrophyte spatial extent identified Submerged macrophytes present at density that perform over time, species and colour. beneficial WQ processes • Distribution of wetlands potentially affected by urban development. Recommend mapping of these wetlands for inclusion in EFG (A) Notes 1. Prior to identification of waterbodies in this classification, there is limited value to nominating indicators. As an exception, a general-purpose indicator is proposed for macrophytes, in line with BWS requirements 2. Amendment from reference to urban lakes and ponds

80 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Urban Ecosystems

Urban streams - naturalised and concrete lined Information Flooding flows, particularly channel maintenance All urban streams within the urban area fall into this flows, are to be protected by restricting abstraction in category, excluding the Molonglo River. Naturalised water management areas to 10% of the flow volume and concrete lined urban streams should be above the 80th percentile. The discharge most considered separately, reflecting the differing critical at determining the width, depth and meander ecological potential of these systems. frequency of channels is the 1.5 to 2.5 year annual recurrence interval flood event. Ecological and other values >> Stormwater function Flow recommendations: >> Transportation of vegetation propagules >> Concrete lined channels: >> Basic ecological function (including connectivity, • Manage flows to reduce runoff volumes, velocities nutrient transfer, etc.) and the transport of pollutants from urban areas to downstream ecosystems.1 PEA/PEF Does not meet the criteria for identification as a PEA or >> Naturalised channels: PEF under MDB Plan Schedules 8 and 9 • Manage flows to reduce runoff volumes, velocities and the transport of pollutants from urban areas BWS to downstream ecosystems.1 Does not meet criteria for consideration • Protect baseflows where baseflow is defined as Flow requirement the modelled natural 80th percentile of stream 2013 EFG flows: flow. Abstractions of surface water may never Baseflows are to be protected: Baseflow is defined as exceed the flow rate. the modelled natural 80th percentile of stream flow • Abstraction of groundwater is limited to 10% of recharge to protect base flows. Abstractions of surface water may never exceed the flow rate. • Protect streams from increased flows caused by urban development. Abstraction of groundwater is limited to 10% of the recharge rate to protect base flow

Objectives Proposed indicators Monitoring Additional objectives: Turbidity does not exceed guidelines for freshwater Currently not To prevent degradation of downstream aquatic ecosystems 80% of the time monitored and ecosystems through sediment deposition and reported2 high flow rates (all reaches)

To maintain healthy aquatic ecosystems in terms • Macroinvertebrate assemblage long-term EFTAG and ACT of biota (all reaches) improvement as measured by AUSRIVAS3 Government to revise • Non-dominance (<20% cover) of in-stream current monitoring 3 macrophytes4 program 1. This measure may require a focus on catchment measures to reduce runoff. 2. It is recommended that monitoring against this objective is considered as part of the review of the ACT water quality monitoring activities. 3. Macroinvertebrate indicator targets of AUSRIVAS Band A may not be achievable in urban streams. A target condition less then Band A may be acceptable within an adaptive management process. 4. Changed from indicator around non-filamentous algae. Macrophytes are a more appropriate measure for naturalised streams

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 81 Urban lakes, ponds and wetlands Information increasing significantly. Therefore the drawdown All lakes, ponds and wetlands within the urban area caused by abstraction, of lakes and ponds constructed excluding the Molonglo River fall into this category. before 2000 can only exceed 0.20m if the activity is Urban lakes, ponds and wetlands are categorised covered by intensive management and monitoring. based on the presence of functional process zones: For minor abstraction activities from lakes and A. Lake – 3 zones/processes ponds, where management/monitoring programs are uneconomical, a drawdown of 0.20m provides an B. Pond – 2 zones efficient and safe limit. C. Wetlands – 1 zone For urban lakes and ponds constructed after 2000 Ecological and other values the maximum drawdown as a result of abstraction >> Waterbirds and their breeding habitat is 0.20m below spillway level, or a lower level if it can >> Amenity/recreation be demonstrated that a pond has been explicitly designed to fulfil its required water quality and >> Vertebrate fauna ecological functions under the proposed drawdown >> Non-potable water supply regime. As with other guidelines, there will be a need >> Algae to monitor the effect of this guideline on lake and pond macrophytes and fish populations of stocked >> Vegetation lakes over time. >> Water quality Flow recommendations: PEA/PEF Allow water level fluctuations of up to 0.60 m below Does not meet the criteria for identification as a PEA or full supply level while continuing to protect waterbird PEF under MDB Plan Schedules 8 and 9 breeding habitat during breeding (drawdown limited to 0.2 m during July to November inclusively).* BWS Presence of significant water-dependent vegetation (*Workshop 1 participants suggested that drawdown of up to 0.8 m below FSL is unlikely to have a detrimental effect on lake Presence of waterbirds macrophytes. There is potentially an effect on flows in urban Flow requirement creeks downstream of the impoundments. A limit of 0.6 m in autumn has been recommended for urban ponds and wetlands. 2013 EFG flows: This is consistent with natural drying patterns in the region and is For urban lakes and ponds that were constructed likely to have benefit for macrophytes and has potential benefit before the year 2000 the drawdown as a result of for denitrification. These waterbodies generally refill rapidly with small rainfall events (Stehlik, 2016) and are located within abstraction is 0.20m below spillway level. ephemeral drainage lines that would benefit from drying out. This level of drawdown would result in the lake There is currently a research project being undertaken by the Institute for Applied Ecology that will inform the effects of water margins retreating approximately 2 metres in most level fluctuations in ponds and wetlands on urban ponds and areas as pond design guidelines require edges to be wetlands.A limit of 0.6 m is also suggested for the larger urban sloped at approximately 1 in 10 for stability, safety lakes, with monitoring of the littoral zone to accompany it. In and public health reasons. Historically it is noted that addition, the effects on the urban creeks downstream of the water level variations without abstraction have been wetlands should be carefully monitored to ensure that there is not a significant effect on baseflows in these streams, with the target greater than 0.20m. Research on Canberra’s lakes and being a more natural streamflow downstream of the urban lakes.) ponds indicates that drawdown to 0.60m is the upper limit without the risk of adverse ecological effects 82 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES Urban lakes, ponds and wetlands

Objectives Proposed indicators Monitoring 2013 EFG objectives: None identified2,3 To maintain healthy aquatic ecosystems in terms of biota

To maintain functional assemblages of Presence of emergent macrophytes of sufficient Littoral zone monitored from macrophytes in urban lakes, ponds and density and diversity to perform beneficial WQ aerial photos, examining wetlands processes and provide habitat for desired fauna. macrophyte spatial extent Submerged macrophytes present at density that over time, species and colour. perform beneficial WQ processes

To protect waterbird breeding habitat from None identified drawdown during breeding season

To maintain populations of fish in urban Fish kills do not occur4 Observation impoundments where stocking occurs 1. Frogs are present in many of these waterbodies, but population health is dominated by land management rather than e-flows. The links between frog abundance and water level are not well established. Urban frog populations are considered under the WSUD code. 2. Macroinvertebrates could be used as an indicator for ecosystem health. Current AUSRIVAS models do not apply to standing waters, but an AUSRIVAS-type model could be constructed for this purpose 3. Monitoring stocked fish for e-flow purposes is not appropriate, however, avoiding draw down to water levels that may induce fish kills will allow maintenance of fish populations.

DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 83 >>